Class Sequel::Dataset
In: lib/sequel/dataset/query.rb
lib/sequel/dataset/features.rb
lib/sequel/dataset/mutation.rb
lib/sequel/dataset/sql.rb
lib/sequel/dataset/placeholder_literalizer.rb
lib/sequel/dataset/prepared_statements.rb
lib/sequel/dataset/graph.rb
lib/sequel/dataset/actions.rb
lib/sequel/dataset/misc.rb
lib/sequel/adapters/sqlite.rb
lib/sequel/adapters/mysql.rb
lib/sequel/adapters/swift.rb
lib/sequel/adapters/sqlanywhere.rb
lib/sequel/adapters/mysql2.rb
lib/sequel/adapters/utils/stored_procedures.rb
lib/sequel/adapters/utils/replace.rb
lib/sequel/dataset.rb
lib/sequel/extensions/query.rb
lib/sequel/extensions/no_auto_literal_strings.rb
lib/sequel/extensions/round_timestamps.rb
lib/sequel/extensions/pagination.rb
lib/sequel/extensions/split_array_nil.rb
lib/sequel/extensions/null_dataset.rb
lib/sequel/extensions/dataset_source_alias.rb
Parent: Object

A dataset represents an SQL query, or more generally, an abstract set of rows in the database. Datasets can be used to create, retrieve, update and delete records.

Query results are always retrieved on demand, so a dataset can be kept around and reused indefinitely (datasets never cache results):

  my_posts = DB[:posts].filter(:author => 'david') # no records are retrieved
  my_posts.all # records are retrieved
  my_posts.all # records are retrieved again

Most dataset methods return modified copies of the dataset (functional style), so you can reuse different datasets to access data:

  posts = DB[:posts]
  davids_posts = posts.filter(:author => 'david')
  old_posts = posts.filter('stamp < ?', Date.today - 7)
  davids_old_posts = davids_posts.filter('stamp < ?', Date.today - 7)

Datasets are Enumerable objects, so they can be manipulated using any of the Enumerable methods, such as map, inject, etc.

For more information, see the "Dataset Basics" guide.

Methods

<<   ==   []   _import   _select_map_multiple   _select_map_single   add_graph_aliases   aliased_expression_sql_append   all   and   array_sql_append   avg   bind   boolean_constant_sql_append   call   call   case_expression_sql_append   cast_sql_append   clause_methods   clone   column_all_sql_append   columns   columns!   complex_expression_sql_append   compound_clone   compound_from_self   constant_sql_append   count   current_datetime   def_mutation_method   def_sql_method   delayed_evaluation_sql_append   delete   distinct   dup   each   each_server   empty?   eql?   escape_like   except   exclude   exclude_having   exclude_where   exists   extension   extension!   fetch_rows   fetch_rows   fetch_rows   fetch_rows   fetch_rows   filter   first   first!   first_source   first_source_alias   first_source_table   for_update   freeze   from   from_self   from_self!   frozen?   function_sql_append   get   graph   graph   grep   group   group_and_count   group_append   group_by   group_cube   group_rollup   grouping_sets   hash   having   identifier_input_method   identifier_input_method=   identifier_output_method   identifier_output_method=   import   insert   insert_sql   inspect   intersect   interval   invert   join   join_clause_sql_append   join_on_clause_sql_append   join_table   join_using_clause_sql_append   joined_dataset?   last   lateral   limit   literal_append   lock_style   map   max   min   multi_insert   multi_insert_sql   naked   naked!   negative_boolean_constant_sql_append   new   offset   options_overlap   or   order   order_append   order_by   order_more   order_prepend   ordered_expression_sql_append   paged_each   paged_each   placeholder_literal_string_sql_append   prepare   prepare   prepare   provides_accurate_rows_matched?   qualified_identifier_sql_append   qualify   quote_identifier_append   quote_identifiers=   quote_identifiers?   quote_schema_table_append   quoted_identifier_append   range   recursive_cte_requires_column_aliases?   register_extension   requires_placeholder_type_specifiers?   requires_sql_standard_datetimes?   returning   reverse   reverse_order   row_number_column   row_proc=   schema_and_table   select   select_all   select_append   select_group   select_hash   select_hash_groups   select_map   select_more   select_order_map   server   server?   set_graph_aliases   simple_select_all?   single_record   single_record!   single_value   single_value!   skip_locked   split_alias   split_multiple_result_sets   split_qualifiers   sql   stream   subscript_sql_append   sum   supports_cte?   supports_cte_in_subqueries?   supports_derived_column_lists?   supports_distinct_on?   supports_group_cube?   supports_group_rollup?   supports_grouping_sets?   supports_insert_select?   supports_intersect_except?   supports_intersect_except_all?   supports_is_true?   supports_join_using?   supports_lateral_subqueries?   supports_limits_in_correlated_subqueries?   supports_modifying_joins?   supports_multiple_column_in?   supports_offsets_in_correlated_subqueries?   supports_ordered_distinct_on?   supports_regexp?   supports_replace?   supports_returning?   supports_select_all_and_column?   supports_skip_locked?   supports_timestamp_timezones?   supports_timestamp_usecs?   supports_where_true?   supports_window_functions?   to_hash   to_hash_groups   to_prepared_statement   truncate   truncate_sql   unbind   unfiltered   ungraphed   ungrouped   union   unlimited   unordered   unqualified_column_for   unused_table_alias   update   update_sql   where   window_sql_append   with   with_recursive   with_sql   with_sql_all   with_sql_delete   with_sql_each   with_sql_first   with_sql_insert   with_sql_single_value   with_sql_update  

Included Modules

1 - Methods that return modified datasets

These methods all return modified copies of the receiver.

Constants

EXTENSIONS = {}   Hash of extension name symbols to callable objects to load the extension into the Dataset object (usually by extending it with a module defined in the extension).
COLUMN_CHANGE_OPTS = [:select, :sql, :from, :join].freeze   The dataset options that require the removal of cached columns if changed.
NON_SQL_OPTIONS = [:server, :defaults, :overrides, :graph, :eager, :eager_graph, :graph_aliases]   Which options don‘t affect the SQL generation. Used by simple_select_all? to determine if this is a simple SELECT * FROM table.
CONDITIONED_JOIN_TYPES = [:inner, :full_outer, :right_outer, :left_outer, :full, :right, :left]   These symbols have _join methods created (e.g. inner_join) that call join_table with the symbol, passing along the arguments and block from the method call.
UNCONDITIONED_JOIN_TYPES = [:natural, :natural_left, :natural_right, :natural_full, :cross]   These symbols have _join methods created (e.g. natural_join). They accept a table argument and options hash which is passed to join_table, and they raise an error if called with a block.
JOIN_METHODS = (CONDITIONED_JOIN_TYPES + UNCONDITIONED_JOIN_TYPES).map{|x| "#{x}_join".to_sym} + [:join, :join_table]   All methods that return modified datasets with a joined table added.
QUERY_METHODS = (<<-METHS).split.map(&:to_sym) + JOIN_METHODS add_graph_aliases and distinct except exclude exclude_having exclude_where filter for_update from from_self graph grep group group_and_count group_append group_by having intersect invert limit lock_style naked offset or order order_append order_by order_more order_prepend qualify reverse reverse_order select select_all select_append select_group select_more server set_graph_aliases unfiltered ungraphed ungrouped union unlimited unordered where with with_recursive with_sql METHS ).split.map(&:to_sym) + JOIN_METHODS   Methods that return modified datasets

Public Class methods

Register an extension callback for Dataset objects. ext should be the extension name symbol, and mod should either be a Module that the dataset is extended with, or a callable object called with the database object. If mod is not provided, a block can be provided and is treated as the mod object.

If mod is a module, this also registers a Database extension that will extend all of the database‘s datasets.

[Source]

    # File lib/sequel/dataset/query.rb, line 55
55:     def self.register_extension(ext, mod=nil, &block)
56:       if mod
57:         raise(Error, "cannot provide both mod and block to Dataset.register_extension") if block
58:         if mod.is_a?(Module)
59:           block = proc{|ds| ds.extend(mod)}
60:           Sequel::Database.register_extension(ext){|db| db.extend_datasets(mod)}
61:         else
62:           block = mod
63:         end
64:       end
65:       Sequel.synchronize{EXTENSIONS[ext] = block}
66:     end

Public Instance methods

Alias for where.

[Source]

    # File lib/sequel/dataset/query.rb, line 69
69:     def and(*cond, &block)
70:       where(*cond, &block)
71:     end

Returns a new clone of the dataset with the given options merged. If the options changed include options in COLUMN_CHANGE_OPTS, the cached columns are deleted. This method should generally not be called directly by user code.

[Source]

    # File lib/sequel/dataset/query.rb, line 77
77:     def clone(opts = nil)
78:       c = super()
79:       if opts
80:         c.instance_variable_set(:@opts, Hash[@opts].merge!(opts))
81:         c.instance_variable_set(:@columns, nil) if @columns && !opts.each_key{|o| break if COLUMN_CHANGE_OPTS.include?(o)}
82:       else
83:         c.instance_variable_set(:@opts, Hash[@opts])
84:       end
85:       c
86:     end

Returns a copy of the dataset with the SQL DISTINCT clause. The DISTINCT clause is used to remove duplicate rows from the output. If arguments are provided, uses a DISTINCT ON clause, in which case it will only be distinct on those columns, instead of all returned columns. If a block is given, it is treated as a virtual row block, similar to where. Raises an error if arguments are given and DISTINCT ON is not supported.

 DB[:items].distinct # SQL: SELECT DISTINCT * FROM items
 DB[:items].order(:id).distinct(:id) # SQL: SELECT DISTINCT ON (id) * FROM items ORDER BY id
 DB[:items].order(:id).distinct{func(:id)} # SQL: SELECT DISTINCT ON (func(id)) * FROM items ORDER BY id

[Source]

     # File lib/sequel/dataset/query.rb, line 98
 98:     def distinct(*args, &block)
 99:       virtual_row_columns(args, block)
100:       raise(InvalidOperation, "DISTINCT ON not supported") if !args.empty? && !supports_distinct_on?
101:       clone(:distinct => args)
102:     end

Adds an EXCEPT clause using a second dataset object. An EXCEPT compound dataset returns all rows in the current dataset that are not in the given dataset. Raises an InvalidOperation if the operation is not supported. Options:

:alias :Use the given value as the from_self alias
:all :Set to true to use EXCEPT ALL instead of EXCEPT, so duplicate rows can occur
:from_self :Set to false to not wrap the returned dataset in a from_self, use with care.
  DB[:items].except(DB[:other_items])
  # SELECT * FROM (SELECT * FROM items EXCEPT SELECT * FROM other_items) AS t1

  DB[:items].except(DB[:other_items], :all=>true, :from_self=>false)
  # SELECT * FROM items EXCEPT ALL SELECT * FROM other_items

  DB[:items].except(DB[:other_items], :alias=>:i)
  # SELECT * FROM (SELECT * FROM items EXCEPT SELECT * FROM other_items) AS i

[Source]

     # File lib/sequel/dataset/query.rb, line 121
121:     def except(dataset, opts=OPTS)
122:       raise(InvalidOperation, "EXCEPT not supported") unless supports_intersect_except?
123:       raise(InvalidOperation, "EXCEPT ALL not supported") if opts[:all] && !supports_intersect_except_all?
124:       compound_clone(:except, dataset, opts)
125:     end

Performs the inverse of Dataset#where. Note that if you have multiple filter conditions, this is not the same as a negation of all conditions.

  DB[:items].exclude(:category => 'software')
  # SELECT * FROM items WHERE (category != 'software')

  DB[:items].exclude(:category => 'software', :id=>3)
  # SELECT * FROM items WHERE ((category != 'software') OR (id != 3))

[Source]

     # File lib/sequel/dataset/query.rb, line 135
135:     def exclude(*cond, &block)
136:       _filter_or_exclude(true, :where, *cond, &block)
137:     end

Inverts the given conditions and adds them to the HAVING clause.

  DB[:items].select_group(:name).exclude_having{count(name) < 2}
  # SELECT name FROM items GROUP BY name HAVING (count(name) >= 2)

[Source]

     # File lib/sequel/dataset/query.rb, line 143
143:     def exclude_having(*cond, &block)
144:       _filter_or_exclude(true, :having, *cond, &block)
145:     end

Alias for exclude.

[Source]

     # File lib/sequel/dataset/query.rb, line 148
148:     def exclude_where(*cond, &block)
149:       exclude(*cond, &block)
150:     end

Return a clone of the dataset loaded with the extensions, see extension!.

[Source]

     # File lib/sequel/dataset/query.rb, line 153
153:     def extension(*exts)
154:       clone.extension!(*exts)
155:     end

Alias for where.

[Source]

     # File lib/sequel/dataset/query.rb, line 158
158:     def filter(*cond, &block)
159:       where(*cond, &block)
160:     end

Returns a cloned dataset with a :update lock style.

  DB[:table].for_update # SELECT * FROM table FOR UPDATE

[Source]

     # File lib/sequel/dataset/query.rb, line 165
165:     def for_update
166:       lock_style(:update)
167:     end

Returns a copy of the dataset with the source changed. If no source is given, removes all tables. If multiple sources are given, it is the same as using a CROSS JOIN (cartesian product) between all tables. If a block is given, it is treated as a virtual row block, similar to where.

  DB[:items].from # SQL: SELECT *
  DB[:items].from(:blah) # SQL: SELECT * FROM blah
  DB[:items].from(:blah, :foo) # SQL: SELECT * FROM blah, foo
  DB[:items].from{fun(arg)} # SQL: SELECT * FROM fun(arg)

[Source]

     # File lib/sequel/dataset/query.rb, line 178
178:     def from(*source, &block)
179:       virtual_row_columns(source, block)
180:       table_alias_num = 0
181:       ctes = nil
182:       source.map! do |s|
183:         case s
184:         when Dataset
185:           if hoist_cte?(s)
186:             ctes ||= []
187:             ctes += s.opts[:with]
188:             s = s.clone(:with=>nil)
189:           end
190:           SQL::AliasedExpression.new(s, dataset_alias(table_alias_num+=1))
191:         when Symbol
192:           sch, table, aliaz = split_symbol(s)
193:           if aliaz
194:             s = sch ? SQL::QualifiedIdentifier.new(sch, table) : SQL::Identifier.new(table)
195:             SQL::AliasedExpression.new(s, aliaz.to_sym)
196:           else
197:             s
198:           end
199:         else
200:           s
201:         end
202:       end
203:       o = {:from=>source.empty? ? nil : source}
204:       o[:with] = (opts[:with] || []) + ctes if ctes
205:       o[:num_dataset_sources] = table_alias_num if table_alias_num > 0
206:       clone(o)
207:     end

Returns a dataset selecting from the current dataset. Supplying the :alias option controls the alias of the result.

  ds = DB[:items].order(:name).select(:id, :name)
  # SELECT id,name FROM items ORDER BY name

  ds.from_self
  # SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS t1

  ds.from_self(:alias=>:foo)
  # SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS foo

  ds.from_self(:alias=>:foo, :column_aliases=>[:c1, :c2])
  # SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS foo(c1, c2)

[Source]

     # File lib/sequel/dataset/query.rb, line 223
223:     def from_self(opts=OPTS)
224:       fs = {}
225:       @opts.keys.each{|k| fs[k] = nil unless NON_SQL_OPTIONS.include?(k)}
226:       clone(fs).from(opts[:alias] ? as(opts[:alias], opts[:column_aliases]) : self)
227:     end

Match any of the columns to any of the patterns. The terms can be strings (which use LIKE) or regular expressions (which are only supported on MySQL and PostgreSQL). Note that the total number of pattern matches will be Array(columns).length * Array(terms).length, which could cause performance issues.

Options (all are boolean):

:all_columns :All columns must be matched to any of the given patterns.
:all_patterns :All patterns must match at least one of the columns.
:case_insensitive :Use a case insensitive pattern match (the default is case sensitive if the database supports it).

If both :all_columns and :all_patterns are true, all columns must match all patterns.

Examples:

  dataset.grep(:a, '%test%')
  # SELECT * FROM items WHERE (a LIKE '%test%' ESCAPE '\')

  dataset.grep([:a, :b], %w'%test% foo')
  # SELECT * FROM items WHERE ((a LIKE '%test%' ESCAPE '\') OR (a LIKE 'foo' ESCAPE '\')
  #   OR (b LIKE '%test%' ESCAPE '\') OR (b LIKE 'foo' ESCAPE '\'))

  dataset.grep([:a, :b], %w'%foo% %bar%', :all_patterns=>true)
  # SELECT * FROM a WHERE (((a LIKE '%foo%' ESCAPE '\') OR (b LIKE '%foo%' ESCAPE '\'))
  #   AND ((a LIKE '%bar%' ESCAPE '\') OR (b LIKE '%bar%' ESCAPE '\')))

  dataset.grep([:a, :b], %w'%foo% %bar%', :all_columns=>true)
  # SELECT * FROM a WHERE (((a LIKE '%foo%' ESCAPE '\') OR (a LIKE '%bar%' ESCAPE '\'))
  #   AND ((b LIKE '%foo%' ESCAPE '\') OR (b LIKE '%bar%' ESCAPE '\')))

  dataset.grep([:a, :b], %w'%foo% %bar%', :all_patterns=>true, :all_columns=>true)
  # SELECT * FROM a WHERE ((a LIKE '%foo%' ESCAPE '\') AND (b LIKE '%foo%' ESCAPE '\')
  #   AND (a LIKE '%bar%' ESCAPE '\') AND (b LIKE '%bar%' ESCAPE '\'))

[Source]

     # File lib/sequel/dataset/query.rb, line 264
264:     def grep(columns, patterns, opts=OPTS)
265:       if opts[:all_patterns]
266:         conds = Array(patterns).map do |pat|
267:           SQL::BooleanExpression.new(opts[:all_columns] ? :AND : :OR, *Array(columns).map{|c| SQL::StringExpression.like(c, pat, opts)})
268:         end
269:         where(SQL::BooleanExpression.new(opts[:all_patterns] ? :AND : :OR, *conds))
270:       else
271:         conds = Array(columns).map do |c|
272:           SQL::BooleanExpression.new(:OR, *Array(patterns).map{|pat| SQL::StringExpression.like(c, pat, opts)})
273:         end
274:         where(SQL::BooleanExpression.new(opts[:all_columns] ? :AND : :OR, *conds))
275:       end
276:     end

Returns a copy of the dataset with the results grouped by the value of the given columns. If a block is given, it is treated as a virtual row block, similar to where.

  DB[:items].group(:id) # SELECT * FROM items GROUP BY id
  DB[:items].group(:id, :name) # SELECT * FROM items GROUP BY id, name
  DB[:items].group{[a, sum(b)]} # SELECT * FROM items GROUP BY a, sum(b)

[Source]

     # File lib/sequel/dataset/query.rb, line 285
285:     def group(*columns, &block)
286:       virtual_row_columns(columns, block)
287:       clone(:group => (columns.compact.empty? ? nil : columns))
288:     end

Returns a dataset grouped by the given column with count by group. Column aliases may be supplied, and will be included in the select clause. If a block is given, it is treated as a virtual row block, similar to where.

Examples:

  DB[:items].group_and_count(:name).all
  # SELECT name, count(*) AS count FROM items GROUP BY name
  # => [{:name=>'a', :count=>1}, ...]

  DB[:items].group_and_count(:first_name, :last_name).all
  # SELECT first_name, last_name, count(*) AS count FROM items GROUP BY first_name, last_name
  # => [{:first_name=>'a', :last_name=>'b', :count=>1}, ...]

  DB[:items].group_and_count(:first_name___name).all
  # SELECT first_name AS name, count(*) AS count FROM items GROUP BY first_name
  # => [{:name=>'a', :count=>1}, ...]

  DB[:items].group_and_count{substr(first_name, 1, 1).as(initial)}.all
  # SELECT substr(first_name, 1, 1) AS initial, count(*) AS count FROM items GROUP BY substr(first_name, 1, 1)
  # => [{:initial=>'a', :count=>1}, ...]

[Source]

     # File lib/sequel/dataset/query.rb, line 316
316:     def group_and_count(*columns, &block)
317:       select_group(*columns, &block).select_more(COUNT_OF_ALL_AS_COUNT)
318:     end

Returns a copy of the dataset with the given columns added to the list of existing columns to group on. If no existing columns are present this method simply sets the columns as the initial ones to group on.

  DB[:items].group_append(:b) # SELECT * FROM items GROUP BY b
  DB[:items].group(:a).group_append(:b) # SELECT * FROM items GROUP BY a, b

[Source]

     # File lib/sequel/dataset/query.rb, line 326
326:     def group_append(*columns, &block)
327:       columns = @opts[:group] + columns if @opts[:group]
328:       group(*columns, &block)
329:     end

Alias of group

[Source]

     # File lib/sequel/dataset/query.rb, line 291
291:     def group_by(*columns, &block)
292:       group(*columns, &block)
293:     end

Adds the appropriate CUBE syntax to GROUP BY.

[Source]

     # File lib/sequel/dataset/query.rb, line 332
332:     def group_cube
333:       raise Error, "GROUP BY CUBE not supported on #{db.database_type}" unless supports_group_cube?
334:       clone(:group_options=>:cube)
335:     end

Adds the appropriate ROLLUP syntax to GROUP BY.

[Source]

     # File lib/sequel/dataset/query.rb, line 338
338:     def group_rollup
339:       raise Error, "GROUP BY ROLLUP not supported on #{db.database_type}" unless supports_group_rollup?
340:       clone(:group_options=>:rollup)
341:     end

Adds the appropriate GROUPING SETS syntax to GROUP BY.

[Source]

     # File lib/sequel/dataset/query.rb, line 344
344:     def grouping_sets
345:       raise Error, "GROUP BY GROUPING SETS not supported on #{db.database_type}" unless supports_grouping_sets?
346:       clone(:group_options=>"grouping sets""grouping sets")
347:     end

Returns a copy of the dataset with the HAVING conditions changed. See where for argument types.

  DB[:items].group(:sum).having(:sum=>10)
  # SELECT * FROM items GROUP BY sum HAVING (sum = 10)

[Source]

     # File lib/sequel/dataset/query.rb, line 353
353:     def having(*cond, &block)
354:       _filter(:having, *cond, &block)
355:     end

Adds an INTERSECT clause using a second dataset object. An INTERSECT compound dataset returns all rows in both the current dataset and the given dataset. Raises an InvalidOperation if the operation is not supported. Options:

:alias :Use the given value as the from_self alias
:all :Set to true to use INTERSECT ALL instead of INTERSECT, so duplicate rows can occur
:from_self :Set to false to not wrap the returned dataset in a from_self, use with care.
  DB[:items].intersect(DB[:other_items])
  # SELECT * FROM (SELECT * FROM items INTERSECT SELECT * FROM other_items) AS t1

  DB[:items].intersect(DB[:other_items], :all=>true, :from_self=>false)
  # SELECT * FROM items INTERSECT ALL SELECT * FROM other_items

  DB[:items].intersect(DB[:other_items], :alias=>:i)
  # SELECT * FROM (SELECT * FROM items INTERSECT SELECT * FROM other_items) AS i

[Source]

     # File lib/sequel/dataset/query.rb, line 374
374:     def intersect(dataset, opts=OPTS)
375:       raise(InvalidOperation, "INTERSECT not supported") unless supports_intersect_except?
376:       raise(InvalidOperation, "INTERSECT ALL not supported") if opts[:all] && !supports_intersect_except_all?
377:       compound_clone(:intersect, dataset, opts)
378:     end

Inverts the current WHERE and HAVING clauses. If there is neither a WHERE or HAVING clause, adds a WHERE clause that is always false.

  DB[:items].where(:category => 'software').invert
  # SELECT * FROM items WHERE (category != 'software')

  DB[:items].where(:category => 'software', :id=>3).invert
  # SELECT * FROM items WHERE ((category != 'software') OR (id != 3))

[Source]

     # File lib/sequel/dataset/query.rb, line 388
388:     def invert
389:       having, where = @opts.values_at(:having, :where)
390:       if having.nil? && where.nil?
391:         where(false)
392:       else
393:         o = {}
394:         o[:having] = SQL::BooleanExpression.invert(having) if having
395:         o[:where] = SQL::BooleanExpression.invert(where) if where
396:         clone(o)
397:       end
398:     end

Alias of inner_join

[Source]

     # File lib/sequel/dataset/query.rb, line 401
401:     def join(*args, &block)
402:       inner_join(*args, &block)
403:     end

Returns a joined dataset. Not usually called directly, users should use the appropriate join method (e.g. join, left_join, natural_join, cross_join) which fills in the type argument.

Takes the following arguments:

type :The type of join to do (e.g. :inner)
table :table to join into the current dataset. Generally one of the following types:
String, Symbol :identifier used as table or view name
Dataset :a subselect is performed with an alias of tN for some value of N
SQL::Function :set returning function
SQL::AliasedExpression :already aliased expression. Uses given alias unless overridden by the :table_alias option.
expr :conditions used when joining, depends on type:
Hash, Array of pairs :Assumes key (1st arg) is column of joined table (unless already qualified), and value (2nd arg) is column of the last joined or primary table (or the :implicit_qualifier option). To specify multiple conditions on a single joined table column, you must use an array. Uses a JOIN with an ON clause.
Array :If all members of the array are symbols, considers them as columns and uses a JOIN with a USING clause. Most databases will remove duplicate columns from the result set if this is used.
nil :If a block is not given, doesn‘t use ON or USING, so the JOIN should be a NATURAL or CROSS join. If a block is given, uses an ON clause based on the block, see below.
otherwise :Treats the argument as a filter expression, so strings are considered literal, symbols specify boolean columns, and Sequel expressions can be used. Uses a JOIN with an ON clause.
options :a hash of options, with the following keys supported:
:table_alias :Override the table alias used when joining. In general you shouldn‘t use this option, you should provide the appropriate SQL::AliasedExpression as the table argument.
:implicit_qualifier :The name to use for qualifying implicit conditions. By default, the last joined or primary table is used.
:reset_implicit_qualifier :Can set to false to ignore this join when future joins determine qualifier for implicit conditions.
:qualify :Can be set to false to not do any implicit qualification. Can be set to :deep to use the Qualifier AST Transformer, which will attempt to qualify subexpressions of the expression tree. Can be set to :symbol to only qualify symbols. Defaults to the value of default_join_table_qualification.
block :The block argument should only be given if a JOIN with an ON clause is used, in which case it yields the table alias/name for the table currently being joined, the table alias/name for the last joined (or first table), and an array of previous SQL::JoinClause. Unlike where, this block is not treated as a virtual row block.

Examples:

  DB[:a].join_table(:cross, :b)
  # SELECT * FROM a CROSS JOIN b

  DB[:a].join_table(:inner, DB[:b], :c=>d)
  # SELECT * FROM a INNER JOIN (SELECT * FROM b) AS t1 ON (t1.c = a.d)

  DB[:a].join_table(:left, :b___c, [:d])
  # SELECT * FROM a LEFT JOIN b AS c USING (d)

  DB[:a].natural_join(:b).join_table(:inner, :c) do |ta, jta, js|
    (Sequel.qualify(ta, :d) > Sequel.qualify(jta, :e)) & {Sequel.qualify(ta, :f)=>DB.from(js.first.table).select(:g)}
  end
  # SELECT * FROM a NATURAL JOIN b INNER JOIN c
  #   ON ((c.d > b.e) AND (c.f IN (SELECT g FROM b)))

[Source]

     # File lib/sequel/dataset/query.rb, line 464
464:     def join_table(type, table, expr=nil, options=OPTS, &block)
465:       if hoist_cte?(table)
466:         s, ds = hoist_cte(table)
467:         return s.join_table(type, ds, expr, options, &block)
468:       end
469: 
470:       using_join = expr.is_a?(Array) && !expr.empty? && expr.all?{|x| x.is_a?(Symbol)}
471:       if using_join && !supports_join_using?
472:         h = {}
473:         expr.each{|e| h[e] = e}
474:         return join_table(type, table, h, options)
475:       end
476: 
477:       table_alias = options[:table_alias]
478:       last_alias = options[:implicit_qualifier]
479:       qualify_type = options[:qualify]
480: 
481:       if table.is_a?(SQL::AliasedExpression)
482:         table_expr = if table_alias
483:           SQL::AliasedExpression.new(table.expression, table_alias, table.columns)
484:         else
485:           table
486:         end
487:         table = table_expr.expression
488:         table_name = table_alias = table_expr.alias
489:       elsif table.is_a?(Dataset)
490:         if table_alias.nil?
491:           table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
492:           table_alias = dataset_alias(table_alias_num)
493:         end
494:         table_name = table_alias
495:         table_expr = SQL::AliasedExpression.new(table, table_alias)
496:       else
497:         table, implicit_table_alias = split_alias(table)
498:         table_alias ||= implicit_table_alias
499:         table_name = table_alias || table
500:         table_expr = table_alias ? SQL::AliasedExpression.new(table, table_alias) : table
501:       end
502: 
503:       join = if expr.nil? and !block
504:         SQL::JoinClause.new(type, table_expr)
505:       elsif using_join
506:         raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block
507:         SQL::JoinUsingClause.new(expr, type, table_expr)
508:       else
509:         last_alias ||= @opts[:last_joined_table] || first_source_alias
510:         if Sequel.condition_specifier?(expr)
511:           expr = expr.collect do |k, v|
512:             qualify_type = default_join_table_qualification if qualify_type.nil?
513:             case qualify_type
514:             when false
515:               nil # Do no qualification
516:             when :deep
517:               k = Sequel::Qualifier.new(self, table_name).transform(k)
518:               v = Sequel::Qualifier.new(self, last_alias).transform(v)
519:             else
520:               k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
521:               v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
522:             end
523:             [k,v]
524:           end
525:           expr = SQL::BooleanExpression.from_value_pairs(expr)
526:         end
527:         if block
528:           expr2 = yield(table_name, last_alias, @opts[:join] || [])
529:           expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
530:         end
531:         SQL::JoinOnClause.new(expr, type, table_expr)
532:       end
533: 
534:       opts = {:join => (@opts[:join] || []) + [join]}
535:       opts[:last_joined_table] = table_name unless options[:reset_implicit_qualifier] == false
536:       opts[:num_dataset_sources] = table_alias_num if table_alias_num
537:       clone(opts)
538:     end

Marks this dataset as a lateral dataset. If used in another dataset‘s FROM or JOIN clauses, it will surround the subquery with LATERAL to enable it to deal with previous tables in the query:

  DB.from(:a, DB[:b].where(:a__c=>:b__d).lateral)
  # SELECT * FROM a, LATERAL (SELECT * FROM b WHERE (a.c = b.d))

[Source]

     # File lib/sequel/dataset/query.rb, line 560
560:     def lateral
561:       clone(:lateral=>true)
562:     end

If given an integer, the dataset will contain only the first l results. If given a range, it will contain only those at offsets within that range. If a second argument is given, it is used as an offset. To use an offset without a limit, pass nil as the first argument.

  DB[:items].limit(10) # SELECT * FROM items LIMIT 10
  DB[:items].limit(10, 20) # SELECT * FROM items LIMIT 10 OFFSET 20
  DB[:items].limit(10...20) # SELECT * FROM items LIMIT 10 OFFSET 10
  DB[:items].limit(10..20) # SELECT * FROM items LIMIT 11 OFFSET 10
  DB[:items].limit(nil, 20) # SELECT * FROM items OFFSET 20

[Source]

     # File lib/sequel/dataset/query.rb, line 574
574:     def limit(l, o = (no_offset = true; nil))
575:       return from_self.limit(l, o) if @opts[:sql]
576: 
577:       if l.is_a?(Range)
578:         no_offset = false
579:         o = l.first
580:         l = l.last - l.first + (l.exclude_end? ? 0 : 1)
581:       end
582:       l = l.to_i if l.is_a?(String) && !l.is_a?(LiteralString)
583:       if l.is_a?(Integer)
584:         raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
585:       end
586: 
587:       ds = clone(:limit=>l)
588:       ds = ds.offset(o) unless no_offset
589:       ds
590:     end

Returns a cloned dataset with the given lock style. If style is a string, it will be used directly. You should never pass a string to this method that is derived from user input, as that can lead to SQL injection.

A symbol may be used for database independent locking behavior, but all supported symbols have separate methods (e.g. for_update).

  DB[:items].lock_style('FOR SHARE NOWAIT')
  # SELECT * FROM items FOR SHARE NOWAIT
  DB[:items].lock_style('FOR UPDATE OF table1 SKIP LOCKED')
  # SELECT * FROM items FOR UPDATE OF table1 SKIP LOCKED

[Source]

     # File lib/sequel/dataset/query.rb, line 604
604:     def lock_style(style)
605:       clone(:lock => style)
606:     end

Returns a cloned dataset without a row_proc.

  ds = DB[:items]
  ds.row_proc = proc(&:invert)
  ds.all # => [{2=>:id}]
  ds.naked.all # => [{:id=>2}]

[Source]

     # File lib/sequel/dataset/query.rb, line 614
614:     def naked
615:       ds = clone
616:       ds.row_proc = nil
617:       ds
618:     end

Returns a copy of the dataset with a specified order. Can be safely combined with limit. If you call limit with an offset, it will override override the offset if you‘ve called offset first.

  DB[:items].offset(10) # SELECT * FROM items OFFSET 10

[Source]

     # File lib/sequel/dataset/query.rb, line 625
625:     def offset(o)
626:       o = o.to_i if o.is_a?(String) && !o.is_a?(LiteralString)
627:       if o.is_a?(Integer)
628:         raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
629:       end
630:       clone(:offset => o)
631:     end

Adds an alternate filter to an existing filter using OR. If no filter exists an Error is raised.

  DB[:items].where(:a).or(:b) # SELECT * FROM items WHERE a OR b

[Source]

     # File lib/sequel/dataset/query.rb, line 637
637:     def or(*cond, &block)
638:       cond = cond.first if cond.size == 1
639:       v = @opts[:where]
640:       if v.nil? || (cond.respond_to?(:empty?) && cond.empty? && !block)
641:         clone
642:       else
643:         clone(:where => SQL::BooleanExpression.new(:OR, v, filter_expr(cond, &block)))
644:       end
645:     end

Returns a copy of the dataset with the order changed. If the dataset has an existing order, it is ignored and overwritten with this order. If a nil is given the returned dataset has no order. This can accept multiple arguments of varying kinds, such as SQL functions. If a block is given, it is treated as a virtual row block, similar to where.

  DB[:items].order(:name) # SELECT * FROM items ORDER BY name
  DB[:items].order(:a, :b) # SELECT * FROM items ORDER BY a, b
  DB[:items].order(Sequel.lit('a + b')) # SELECT * FROM items ORDER BY a + b
  DB[:items].order(:a + :b) # SELECT * FROM items ORDER BY (a + b)
  DB[:items].order(Sequel.desc(:name)) # SELECT * FROM items ORDER BY name DESC
  DB[:items].order(Sequel.asc(:name, :nulls=>:last)) # SELECT * FROM items ORDER BY name ASC NULLS LAST
  DB[:items].order{sum(name).desc} # SELECT * FROM items ORDER BY sum(name) DESC
  DB[:items].order(nil) # SELECT * FROM items

[Source]

     # File lib/sequel/dataset/query.rb, line 661
661:     def order(*columns, &block)
662:       virtual_row_columns(columns, block)
663:       clone(:order => (columns.compact.empty?) ? nil : columns)
664:     end

Alias of order_more, for naming consistency with order_prepend.

[Source]

     # File lib/sequel/dataset/query.rb, line 667
667:     def order_append(*columns, &block)
668:       order_more(*columns, &block)
669:     end

Alias of order

[Source]

     # File lib/sequel/dataset/query.rb, line 672
672:     def order_by(*columns, &block)
673:       order(*columns, &block)
674:     end

Returns a copy of the dataset with the order columns added to the end of the existing order.

  DB[:items].order(:a).order(:b) # SELECT * FROM items ORDER BY b
  DB[:items].order(:a).order_more(:b) # SELECT * FROM items ORDER BY a, b

[Source]

     # File lib/sequel/dataset/query.rb, line 681
681:     def order_more(*columns, &block)
682:       columns = @opts[:order] + columns if @opts[:order]
683:       order(*columns, &block)
684:     end

Returns a copy of the dataset with the order columns added to the beginning of the existing order.

  DB[:items].order(:a).order(:b) # SELECT * FROM items ORDER BY b
  DB[:items].order(:a).order_prepend(:b) # SELECT * FROM items ORDER BY b, a

[Source]

     # File lib/sequel/dataset/query.rb, line 691
691:     def order_prepend(*columns, &block)
692:       ds = order(*columns, &block)
693:       @opts[:order] ? ds.order_more(*@opts[:order]) : ds
694:     end

Qualify to the given table, or first source if no table is given.

  DB[:items].where(:id=>1).qualify
  # SELECT items.* FROM items WHERE (items.id = 1)

  DB[:items].where(:id=>1).qualify(:i)
  # SELECT i.* FROM items WHERE (i.id = 1)

[Source]

     # File lib/sequel/dataset/query.rb, line 703
703:     def qualify(table=first_source)
704:       o = @opts
705:       return clone if o[:sql]
706:       h = {}
707:       (o.keys & QUALIFY_KEYS).each do |k|
708:         h[k] = qualified_expression(o[k], table)
709:       end
710:       h[:select] = [SQL::ColumnAll.new(table)] if !o[:select] || o[:select].empty?
711:       clone(h)
712:     end

Modify the RETURNING clause, only supported on a few databases. If returning is used, instead of insert returning the autogenerated primary key or update/delete returning the number of modified rows, results are returned using fetch_rows.

  DB[:items].returning # RETURNING *
  DB[:items].returning(nil) # RETURNING NULL
  DB[:items].returning(:id, :name) # RETURNING id, name

[Source]

     # File lib/sequel/dataset/query.rb, line 722
722:     def returning(*values)
723:       raise Error, "RETURNING is not supported on #{db.database_type}" unless supports_returning?(:insert)
724:       clone(:returning=>values)
725:     end

Returns a copy of the dataset with the order reversed. If no order is given, the existing order is inverted.

  DB[:items].reverse(:id) # SELECT * FROM items ORDER BY id DESC
  DB[:items].reverse{foo(bar)} # SELECT * FROM items ORDER BY foo(bar) DESC
  DB[:items].order(:id).reverse # SELECT * FROM items ORDER BY id DESC
  DB[:items].order(:id).reverse(Sequel.desc(:name)) # SELECT * FROM items ORDER BY name ASC

[Source]

     # File lib/sequel/dataset/query.rb, line 734
734:     def reverse(*order, &block)
735:       virtual_row_columns(order, block)
736:       order(*invert_order(order.empty? ? @opts[:order] : order))
737:     end

Alias of reverse

[Source]

     # File lib/sequel/dataset/query.rb, line 740
740:     def reverse_order(*order, &block)
741:       reverse(*order, &block)
742:     end

Returns a copy of the dataset with the columns selected changed to the given columns. This also takes a virtual row block, similar to where.

  DB[:items].select(:a) # SELECT a FROM items
  DB[:items].select(:a, :b) # SELECT a, b FROM items
  DB[:items].select{[a, sum(b)]} # SELECT a, sum(b) FROM items

[Source]

     # File lib/sequel/dataset/query.rb, line 751
751:     def select(*columns, &block)
752:       virtual_row_columns(columns, block)
753:       clone(:select => columns)
754:     end

Returns a copy of the dataset selecting the wildcard if no arguments are given. If arguments are given, treat them as tables and select all columns (using the wildcard) from each table.

  DB[:items].select(:a).select_all # SELECT * FROM items
  DB[:items].select_all(:items) # SELECT items.* FROM items
  DB[:items].select_all(:items, :foo) # SELECT items.*, foo.* FROM items

[Source]

     # File lib/sequel/dataset/query.rb, line 763
763:     def select_all(*tables)
764:       if tables.empty?
765:         clone(:select => nil)
766:       else
767:         select(*tables.map{|t| i, a = split_alias(t); a || i}.map{|t| SQL::ColumnAll.new(t)})
768:       end
769:     end

Returns a copy of the dataset with the given columns added to the existing selected columns. If no columns are currently selected, it will select the columns given in addition to *.

  DB[:items].select(:a).select(:b) # SELECT b FROM items
  DB[:items].select(:a).select_append(:b) # SELECT a, b FROM items
  DB[:items].select_append(:b) # SELECT *, b FROM items

[Source]

     # File lib/sequel/dataset/query.rb, line 778
778:     def select_append(*columns, &block)
779:       cur_sel = @opts[:select]
780:       if !cur_sel || cur_sel.empty?
781:         unless supports_select_all_and_column?
782:           return select_all(*(Array(@opts[:from]) + Array(@opts[:join]))).select_more(*columns, &block)
783:         end
784:         cur_sel = [WILDCARD]
785:       end
786:       select(*(cur_sel + columns), &block)
787:     end

Set both the select and group clauses with the given columns. Column aliases may be supplied, and will be included in the select clause. This also takes a virtual row block similar to where.

  DB[:items].select_group(:a, :b)
  # SELECT a, b FROM items GROUP BY a, b

  DB[:items].select_group(:c___a){f(c2)}
  # SELECT c AS a, f(c2) FROM items GROUP BY c, f(c2)

[Source]

     # File lib/sequel/dataset/query.rb, line 798
798:     def select_group(*columns, &block)
799:       virtual_row_columns(columns, block)
800:       select(*columns).group(*columns.map{|c| unaliased_identifier(c)})
801:     end

Alias for select_append.

[Source]

     # File lib/sequel/dataset/query.rb, line 804
804:     def select_more(*columns, &block)
805:       select_append(*columns, &block)
806:     end

Set the server for this dataset to use. Used to pick a specific database shard to run a query against, or to override the default (where SELECT uses :read_only database and all other queries use the :default database). This method is always available but is only useful when database sharding is being used.

  DB[:items].all # Uses the :read_only or :default server
  DB[:items].delete # Uses the :default server
  DB[:items].server(:blah).delete # Uses the :blah server

[Source]

     # File lib/sequel/dataset/query.rb, line 817
817:     def server(servr)
818:       clone(:server=>servr)
819:     end

If the database uses sharding and the current dataset has not had a server set, return a cloned dataset that uses the given server. Otherwise, return the receiver directly instead of returning a clone.

[Source]

     # File lib/sequel/dataset/query.rb, line 824
824:     def server?(server)
825:       if db.sharded? && !opts[:server]
826:         server(server)
827:       else
828:         self
829:       end
830:     end

Skip locked rows when returning results from this dataset.

[Source]

     # File lib/sequel/dataset/query.rb, line 833
833:     def skip_locked
834:       raise(Error, 'This dataset does not support skipping locked rows') unless supports_skip_locked?
835:       clone(:skip_locked=>true)
836:     end

Unbind bound variables from this dataset‘s filter and return an array of two objects. The first object is a modified dataset where the filter has been replaced with one that uses bound variable placeholders. The second object is the hash of unbound variables. You can then prepare and execute (or just call) the dataset with the bound variables to get results.

  ds, bv = DB[:items].where(:a=>1).unbind
  ds # SELECT * FROM items WHERE (a = $a)
  bv #  {:a => 1}
  ds.call(:select, bv)

[Source]

     # File lib/sequel/dataset/query.rb, line 848
848:     def unbind
849:       u = Unbinder.new
850:       ds = clone(:where=>u.transform(opts[:where]), :join=>u.transform(opts[:join]))
851:       [ds, u.binds]
852:     end

Returns a copy of the dataset with no filters (HAVING or WHERE clause) applied.

  DB[:items].group(:a).having(:a=>1).where(:b).unfiltered
  # SELECT * FROM items GROUP BY a

[Source]

     # File lib/sequel/dataset/query.rb, line 858
858:     def unfiltered
859:       clone(:where => nil, :having => nil)
860:     end

Returns a copy of the dataset with no grouping (GROUP or HAVING clause) applied.

  DB[:items].group(:a).having(:a=>1).where(:b).ungrouped
  # SELECT * FROM items WHERE b

[Source]

     # File lib/sequel/dataset/query.rb, line 866
866:     def ungrouped
867:       clone(:group => nil, :having => nil)
868:     end

Adds a UNION clause using a second dataset object. A UNION compound dataset returns all rows in either the current dataset or the given dataset. Options:

:alias :Use the given value as the from_self alias
:all :Set to true to use UNION ALL instead of UNION, so duplicate rows can occur
:from_self :Set to false to not wrap the returned dataset in a from_self, use with care.
  DB[:items].union(DB[:other_items])
  # SELECT * FROM (SELECT * FROM items UNION SELECT * FROM other_items) AS t1

  DB[:items].union(DB[:other_items], :all=>true, :from_self=>false)
  # SELECT * FROM items UNION ALL SELECT * FROM other_items

  DB[:items].union(DB[:other_items], :alias=>:i)
  # SELECT * FROM (SELECT * FROM items UNION SELECT * FROM other_items) AS i

[Source]

     # File lib/sequel/dataset/query.rb, line 886
886:     def union(dataset, opts=OPTS)
887:       compound_clone(:union, dataset, opts)
888:     end

Returns a copy of the dataset with no limit or offset.

  DB[:items].limit(10, 20).unlimited # SELECT * FROM items

[Source]

     # File lib/sequel/dataset/query.rb, line 893
893:     def unlimited
894:       clone(:limit=>nil, :offset=>nil)
895:     end

Returns a copy of the dataset with no order.

  DB[:items].order(:a).unordered # SELECT * FROM items

[Source]

     # File lib/sequel/dataset/query.rb, line 900
900:     def unordered
901:       order(nil)
902:     end

Returns a copy of the dataset with the given WHERE conditions imposed upon it.

Accepts the following argument types:

Hash :list of equality/inclusion expressions
Array :depends:
  • If first member is a string, assumes the rest of the arguments are parameters and interpolates them into the string.
  • If all members are arrays of length two, treats the same way as a hash, except it allows for duplicate keys to be specified.
  • Otherwise, treats each argument as a separate condition.
String :taken literally
Symbol :taken as a boolean column argument (e.g. WHERE active)
Sequel::SQL::BooleanExpression :an existing condition expression, probably created using the Sequel expression filter DSL.

where also accepts a block, which should return one of the above argument types, and is treated the same way. This block yields a virtual row object, which is easy to use to create identifiers and functions. For more details on the virtual row support, see the "Virtual Rows" guide

If both a block and regular argument are provided, they get ANDed together.

Examples:

  DB[:items].where(:id => 3)
  # SELECT * FROM items WHERE (id = 3)

  DB[:items].where('price < ?', 100)
  # SELECT * FROM items WHERE price < 100

  DB[:items].where([[:id, [1,2,3]], [:id, 0..10]])
  # SELECT * FROM items WHERE ((id IN (1, 2, 3)) AND ((id >= 0) AND (id <= 10)))

  DB[:items].where('price < 100')
  # SELECT * FROM items WHERE price < 100

  DB[:items].where(:active)
  # SELECT * FROM items WHERE :active

  DB[:items].where{price < 100}
  # SELECT * FROM items WHERE (price < 100)

Multiple where calls can be chained for scoping:

  software = dataset.where(:category => 'software').where{price < 100}
  # SELECT * FROM items WHERE ((category = 'software') AND (price < 100))

See the "Dataset Filtering" guide for more examples and details.

[Source]

     # File lib/sequel/dataset/query.rb, line 954
954:     def where(*cond, &block)
955:       _filter(:where, *cond, &block)
956:     end

Add a common table expression (CTE) with the given name and a dataset that defines the CTE. A common table expression acts as an inline view for the query. Options:

:args :Specify the arguments/columns for the CTE, should be an array of symbols.
:recursive :Specify that this is a recursive CTE
  DB[:items].with(:items, DB[:syx].where(:name.like('A%')))
  # WITH items AS (SELECT * FROM syx WHERE (name LIKE 'A%' ESCAPE '\')) SELECT * FROM items

[Source]

     # File lib/sequel/dataset/query.rb, line 966
966:     def with(name, dataset, opts=OPTS)
967:       raise(Error, 'This dataset does not support common table expressions') unless supports_cte?
968:       if hoist_cte?(dataset)
969:         s, ds = hoist_cte(dataset)
970:         s.with(name, ds, opts)
971:       else
972:         clone(:with=>(@opts[:with]||[]) + [Hash[opts].merge!(:name=>name, :dataset=>dataset)])
973:       end
974:     end

Add a recursive common table expression (CTE) with the given name, a dataset that defines the nonrecursive part of the CTE, and a dataset that defines the recursive part of the CTE. Options:

:args :Specify the arguments/columns for the CTE, should be an array of symbols.
:union_all :Set to false to use UNION instead of UNION ALL combining the nonrecursive and recursive parts.
  DB[:t].with_recursive(:t,
    DB[:i1].select(:id, :parent_id).where(:parent_id=>nil),
    DB[:i1].join(:t, :id=>:parent_id).select(:i1__id, :i1__parent_id),
    :args=>[:id, :parent_id])

  # WITH RECURSIVE "t"("id", "parent_id") AS (
  #   SELECT "id", "parent_id" FROM "i1" WHERE ("parent_id" IS NULL)
  #   UNION ALL
  #   SELECT "i1"."id", "i1"."parent_id" FROM "i1" INNER JOIN "t" ON ("t"."id" = "i1"."parent_id")
  # ) SELECT * FROM "t"

[Source]

      # File lib/sequel/dataset/query.rb, line 992
 992:     def with_recursive(name, nonrecursive, recursive, opts=OPTS)
 993:       raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
 994:       if hoist_cte?(nonrecursive)
 995:         s, ds = hoist_cte(nonrecursive)
 996:         s.with_recursive(name, ds, recursive, opts)
 997:       elsif hoist_cte?(recursive)
 998:         s, ds = hoist_cte(recursive)
 999:         s.with_recursive(name, nonrecursive, ds, opts)
1000:       else
1001:         clone(:with=>(@opts[:with]||[]) + [Hash[opts].merge!(:recursive=>true, :name=>name, :dataset=>nonrecursive.union(recursive, {:all=>opts[:union_all] != false, :from_self=>false}))])
1002:       end
1003:     end

Returns a copy of the dataset with the static SQL used. This is useful if you want to keep the same row_proc/graph, but change the SQL used to custom SQL.

  DB[:items].with_sql('SELECT * FROM foo') # SELECT * FROM foo

You can use placeholders in your SQL and provide arguments for those placeholders:

  DB[:items].with_sql('SELECT ? FROM foo', 1) # SELECT 1 FROM foo

You can also provide a method name and arguments to call to get the SQL:

  DB[:items].with_sql(:insert_sql, :b=>1) # INSERT INTO items (b) VALUES (1)

[Source]

      # File lib/sequel/dataset/query.rb, line 1017
1017:     def with_sql(sql, *args)
1018:       if sql.is_a?(Symbol)
1019:         sql = send(sql, *args)
1020:       else
1021:         sql = SQL::PlaceholderLiteralString.new(sql, args) unless args.empty?
1022:       end
1023:       clone(:sql=>sql)
1024:     end

Protected Instance methods

Add the dataset to the list of compounds

[Source]

      # File lib/sequel/dataset/query.rb, line 1029
1029:     def compound_clone(type, dataset, opts)
1030:       if hoist_cte?(dataset)
1031:         s, ds = hoist_cte(dataset)
1032:         return s.compound_clone(type, ds, opts)
1033:       end
1034:       ds = compound_from_self.clone(:compounds=>Array(@opts[:compounds]).map(&:dup) + [[type, dataset.compound_from_self, opts[:all]]])
1035:       opts[:from_self] == false ? ds : ds.from_self(opts)
1036:     end

Return true if the dataset has a non-nil value for any key in opts.

[Source]

      # File lib/sequel/dataset/query.rb, line 1039
1039:     def options_overlap(opts)
1040:       !(@opts.collect{|k,v| k unless v.nil?}.compact & opts).empty?
1041:     end

Whether this dataset is a simple select from an underlying table, such as:

  SELECT * FROM table
  SELECT table.* FROM table

[Source]

      # File lib/sequel/dataset/query.rb, line 1047
1047:     def simple_select_all?
1048:       o = @opts.reject{|k,v| v.nil? || NON_SQL_OPTIONS.include?(k)}
1049:       if (f = o[:from]) && f.length == 1 && (f.first.is_a?(Symbol) || f.first.is_a?(SQL::AliasedExpression))
1050:         case o.length
1051:         when 1
1052:           true
1053:         when 2
1054:           (s = o[:select]) && s.length == 1 && s.first.is_a?(SQL::ColumnAll)
1055:         else
1056:           false
1057:         end
1058:       else
1059:         false
1060:       end
1061:     end

4 - Methods that describe what the dataset supports

These methods all return booleans, with most describing whether or not the dataset supports a feature.

Public Instance methods

Whether this dataset will provide accurate number of rows matched for delete and update statements. Accurate in this case is the number of rows matched by the dataset‘s filter.

[Source]

    # File lib/sequel/dataset/features.rb, line 23
23:     def provides_accurate_rows_matched?
24:       true
25:     end

Whether this dataset quotes identifiers.

[Source]

    # File lib/sequel/dataset/features.rb, line 12
12:     def quote_identifiers?
13:       if defined?(@quote_identifiers)
14:         @quote_identifiers
15:       else
16:         @quote_identifiers = db.quote_identifiers?
17:       end
18:     end

Whether you must use a column alias list for recursive CTEs (false by default).

[Source]

    # File lib/sequel/dataset/features.rb, line 29
29:     def recursive_cte_requires_column_aliases?
30:       false
31:     end

Whether type specifiers are required for prepared statement/bound variable argument placeholders (i.e. :bv__integer)

[Source]

    # File lib/sequel/dataset/features.rb, line 41
41:     def requires_placeholder_type_specifiers?
42:       false
43:     end

Whether the dataset requires SQL standard datetimes (false by default, as most allow strings with ISO 8601 format).

[Source]

    # File lib/sequel/dataset/features.rb, line 35
35:     def requires_sql_standard_datetimes?
36:       false
37:     end

Whether the dataset supports common table expressions (the WITH clause). If given, type can be :select, :insert, :update, or :delete, in which case it determines whether WITH is supported for the respective statement type.

[Source]

    # File lib/sequel/dataset/features.rb, line 48
48:     def supports_cte?(type=:select)
49:       false
50:     end

Whether the dataset supports common table expressions (the WITH clause) in subqueries. If false, applies the WITH clause to the main query, which can cause issues if multiple WITH clauses use the same name.

[Source]

    # File lib/sequel/dataset/features.rb, line 55
55:     def supports_cte_in_subqueries?
56:       false
57:     end

Whether the database supports derived column lists (e.g. "table_expr AS table_alias(column_alias1, column_alias2, …)"), true by default.

[Source]

    # File lib/sequel/dataset/features.rb, line 62
62:     def supports_derived_column_lists?
63:       true
64:     end

Whether the dataset supports or can emulate the DISTINCT ON clause, false by default.

[Source]

    # File lib/sequel/dataset/features.rb, line 67
67:     def supports_distinct_on?
68:       false
69:     end

Whether the dataset supports CUBE with GROUP BY.

[Source]

    # File lib/sequel/dataset/features.rb, line 72
72:     def supports_group_cube?
73:       false
74:     end

Whether the dataset supports ROLLUP with GROUP BY.

[Source]

    # File lib/sequel/dataset/features.rb, line 77
77:     def supports_group_rollup?
78:       false
79:     end

Whether the dataset supports GROUPING SETS with GROUP BY.

[Source]

    # File lib/sequel/dataset/features.rb, line 82
82:     def supports_grouping_sets?
83:       false
84:     end

Whether this dataset supports the insert_select method for returning all columns values directly from an insert query.

[Source]

    # File lib/sequel/dataset/features.rb, line 88
88:     def supports_insert_select?
89:       supports_returning?(:insert)
90:     end

Whether the dataset supports the INTERSECT and EXCEPT compound operations, true by default.

[Source]

    # File lib/sequel/dataset/features.rb, line 93
93:     def supports_intersect_except?
94:       true
95:     end

Whether the dataset supports the INTERSECT ALL and EXCEPT ALL compound operations, true by default.

[Source]

     # File lib/sequel/dataset/features.rb, line 98
 98:     def supports_intersect_except_all?
 99:       true
100:     end

Whether the dataset supports the IS TRUE syntax.

[Source]

     # File lib/sequel/dataset/features.rb, line 103
103:     def supports_is_true?
104:       true
105:     end

Whether the dataset supports the JOIN table USING (column1, …) syntax.

[Source]

     # File lib/sequel/dataset/features.rb, line 108
108:     def supports_join_using?
109:       true
110:     end

Whether the dataset supports LATERAL for subqueries in the FROM or JOIN clauses.

[Source]

     # File lib/sequel/dataset/features.rb, line 113
113:     def supports_lateral_subqueries?
114:       false
115:     end

Whether limits are supported in correlated subqueries. True by default.

[Source]

     # File lib/sequel/dataset/features.rb, line 118
118:     def supports_limits_in_correlated_subqueries?
119:       true
120:     end

Whether modifying joined datasets is supported.

[Source]

     # File lib/sequel/dataset/features.rb, line 123
123:     def supports_modifying_joins?
124:       false
125:     end

Whether the IN/NOT IN operators support multiple columns when an array of values is given.

[Source]

     # File lib/sequel/dataset/features.rb, line 129
129:     def supports_multiple_column_in?
130:       true
131:     end

Whether offsets are supported in correlated subqueries, true by default.

[Source]

     # File lib/sequel/dataset/features.rb, line 134
134:     def supports_offsets_in_correlated_subqueries?
135:       true
136:     end

Whether the dataset supports or can fully emulate the DISTINCT ON clause, including respecting the ORDER BY clause, false by default

[Source]

     # File lib/sequel/dataset/features.rb, line 140
140:     def supports_ordered_distinct_on?
141:       supports_distinct_on?
142:     end

Whether the dataset supports pattern matching by regular expressions.

[Source]

     # File lib/sequel/dataset/features.rb, line 145
145:     def supports_regexp?
146:       false
147:     end

Whether the dataset supports REPLACE syntax, false by default.

[Source]

     # File lib/sequel/dataset/features.rb, line 150
150:     def supports_replace?
151:       false
152:     end

Whether the RETURNING clause is supported for the given type of query. type can be :insert, :update, or :delete.

[Source]

     # File lib/sequel/dataset/features.rb, line 156
156:     def supports_returning?(type)
157:       false
158:     end

Whether the database supports SELECT *, column FROM table

[Source]

     # File lib/sequel/dataset/features.rb, line 166
166:     def supports_select_all_and_column?
167:       true
168:     end

Whether the dataset supports skipping locked rows when returning data.

[Source]

     # File lib/sequel/dataset/features.rb, line 161
161:     def supports_skip_locked?
162:       false
163:     end

Whether the dataset supports timezones in literal timestamps

[Source]

     # File lib/sequel/dataset/features.rb, line 171
171:     def supports_timestamp_timezones?
172:       false
173:     end

Whether the dataset supports fractional seconds in literal timestamps

[Source]

     # File lib/sequel/dataset/features.rb, line 176
176:     def supports_timestamp_usecs?
177:       true
178:     end

Whether the dataset supports WHERE TRUE (or WHERE 1 for databases that that use 1 for true).

[Source]

     # File lib/sequel/dataset/features.rb, line 187
187:     def supports_where_true?
188:       true
189:     end

Whether the dataset supports window functions.

[Source]

     # File lib/sequel/dataset/features.rb, line 181
181:     def supports_window_functions?
182:       false
183:     end

7 - Mutation methods

These methods modify the receiving dataset and should be used with care.

Constants

MUTATION_METHODS = QUERY_METHODS - [:naked, :from_self]   All methods that should have a ! method added that modifies the receiver.

Attributes

row_proc  [R]  The row_proc for this database, should be any object that responds to call with a single hash argument and returns the object you want each to return.

Public Class methods

Setup mutation (e.g. filter!) methods. These operate the same as the non-! methods, but replace the options of the current dataset with the options of the resulting dataset.

Do not call this method with untrusted input, as that can result in arbitrary code execution.

[Source]

    # File lib/sequel/dataset/mutation.rb, line 19
19:     def self.def_mutation_method(*meths)
20:       options = meths.pop if meths.last.is_a?(Hash)
21:       mod = options[:module] if options
22:       mod ||= self
23:       meths.each do |meth|
24:         mod.class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
25:       end
26:     end

Public Instance methods

Load an extension into the receiver. In addition to requiring the extension file, this also modifies the dataset to work with the extension (usually extending it with a module defined in the extension file). If no related extension file exists or the extension does not have specific support for Database objects, an Error will be raised. Returns self.

[Source]

    # File lib/sequel/dataset/mutation.rb, line 40
40:     def extension!(*exts)
41:       raise_if_frozen!
42:       Sequel.extension(*exts)
43:       exts.each do |ext|
44:         if pr = Sequel.synchronize{EXTENSIONS[ext]}
45:           pr.call(self)
46:         else
47:           raise(Error, "Extension #{ext} does not have specific support handling individual datasets (try: Sequel.extension #{ext.inspect})")
48:         end
49:       end
50:       self
51:     end

Avoid self-referential dataset by cloning.

[Source]

    # File lib/sequel/dataset/mutation.rb, line 54
54:     def from_self!(*args, &block)
55:       raise_if_frozen!
56:       @opts = clone.from_self(*args, &block).opts
57:       self
58:     end

Set the method to call on identifiers going into the database for this dataset

[Source]

    # File lib/sequel/dataset/mutation.rb, line 61
61:     def identifier_input_method=(v)
62:       raise_if_frozen!
63:       skip_symbol_cache!
64:       @identifier_input_method = v
65:     end

Set the method to call on identifiers coming the database for this dataset

[Source]

    # File lib/sequel/dataset/mutation.rb, line 68
68:     def identifier_output_method=(v)
69:       raise_if_frozen!
70:       @identifier_output_method = v
71:     end

Remove the row_proc from the current dataset.

[Source]

    # File lib/sequel/dataset/mutation.rb, line 74
74:     def naked!
75:       raise_if_frozen!
76:       self.row_proc = nil
77:       self
78:     end

Set whether to quote identifiers for this dataset

[Source]

    # File lib/sequel/dataset/mutation.rb, line 81
81:     def quote_identifiers=(v)
82:       raise_if_frozen!
83:       skip_symbol_cache!
84:       @quote_identifiers = v
85:     end

Override the row_proc for this dataset

[Source]

    # File lib/sequel/dataset/mutation.rb, line 88
88:     def row_proc=(v)
89:       raise_if_frozen!
90:       @row_proc = v
91:     end

3 - User Methods relating to SQL Creation

These are methods you can call to see what SQL will be generated by the dataset.

Public Instance methods

Returns an EXISTS clause for the dataset as an SQL::PlaceholderLiteralString.

  DB.select(1).where(DB[:items].exists)
  # SELECT 1 WHERE (EXISTS (SELECT * FROM items))

[Source]

    # File lib/sequel/dataset/sql.rb, line 14
14:     def exists
15:       SQL::PlaceholderLiteralString.new(EXISTS, [self], true)
16:     end

Returns an INSERT SQL query string. See insert.

  DB[:items].insert_sql(:a=>1)
  # => "INSERT INTO items (a) VALUES (1)"

[Source]

    # File lib/sequel/dataset/sql.rb, line 22
22:     def insert_sql(*values)
23:       return static_sql(@opts[:sql]) if @opts[:sql]
24: 
25:       check_modification_allowed!
26: 
27:       columns = []
28: 
29:       case values.size
30:       when 0
31:         return insert_sql({})
32:       when 1
33:         case vals = values.at(0)
34:         when Hash
35:           values = []
36:           vals.each do |k,v| 
37:             columns << k
38:             values << v
39:           end
40:         when Dataset, Array, LiteralString
41:           values = vals
42:         end
43:       when 2
44:         if (v0 = values.at(0)).is_a?(Array) && ((v1 = values.at(1)).is_a?(Array) || v1.is_a?(Dataset) || v1.is_a?(LiteralString))
45:           columns, values = v0, v1
46:           raise(Error, "Different number of values and columns given to insert_sql") if values.is_a?(Array) and columns.length != values.length
47:         end
48:       end
49: 
50:       if values.is_a?(Array) && values.empty? && !insert_supports_empty_values? 
51:         columns, values = insert_empty_columns_values
52:       end
53:       clone(:columns=>columns, :values=>values).send(:_insert_sql)
54:     end

Append a literal representation of a value to the given SQL string.

If an unsupported object is given, an Error is raised.

[Source]

     # File lib/sequel/dataset/sql.rb, line 59
 59:     def literal_append(sql, v)
 60:       case v
 61:       when Symbol
 62:         if skip_symbol_cache?
 63:           literal_symbol_append(sql, v)
 64:         else 
 65:           unless l = db.literal_symbol(v)
 66:             l = String.new
 67:             literal_symbol_append(l, v)
 68:             db.literal_symbol_set(v, l)
 69:           end
 70:           sql << l
 71:         end
 72:       when String
 73:         case v
 74:         when LiteralString
 75:           sql << v
 76:         when SQL::Blob
 77:           literal_blob_append(sql, v)
 78:         else
 79:           literal_string_append(sql, v)
 80:         end
 81:       when Integer
 82:         sql << literal_integer(v)
 83:       when Hash
 84:         literal_hash_append(sql, v)
 85:       when SQL::Expression
 86:         literal_expression_append(sql, v)
 87:       when Float
 88:         sql << literal_float(v)
 89:       when BigDecimal
 90:         sql << literal_big_decimal(v)
 91:       when NilClass
 92:         sql << literal_nil
 93:       when TrueClass
 94:         sql << literal_true
 95:       when FalseClass
 96:         sql << literal_false
 97:       when Array
 98:         literal_array_append(sql, v)
 99:       when Time
100:         v.is_a?(SQLTime) ? literal_sqltime_append(sql, v) : literal_time_append(sql, v)
101:       when DateTime
102:         literal_datetime_append(sql, v)
103:       when Date
104:         sql << literal_date(v)
105:       when Dataset
106:         literal_dataset_append(sql, v)
107:       else
108:         literal_other_append(sql, v)
109:       end
110:     end

Returns an array of insert statements for inserting multiple records. This method is used by multi_insert to format insert statements and expects a keys array and and an array of value arrays.

This method should be overridden by descendants if the support inserting multiple records in a single SQL statement.

[Source]

     # File lib/sequel/dataset/sql.rb, line 118
118:     def multi_insert_sql(columns, values)
119:       case multi_insert_sql_strategy
120:       when :values
121:         sql = LiteralString.new('VALUES ')
122:         expression_list_append(sql, values.map{|r| Array(r)})
123:         [insert_sql(columns, sql)]
124:       when :union
125:         c = false
126:         sql = LiteralString.new
127:         u = UNION_ALL_SELECT
128:         f = empty_from_sql
129:         values.each do |v|
130:           if c
131:             sql << u
132:           else
133:             sql << SELECT << SPACE
134:             c = true
135:           end
136:           expression_list_append(sql, v)
137:           sql << f if f
138:         end
139:         [insert_sql(columns, sql)]
140:       else
141:         values.map{|r| insert_sql(columns, r)}
142:       end
143:     end

Same as select_sql, not aliased directly to make subclassing simpler.

[Source]

     # File lib/sequel/dataset/sql.rb, line 146
146:     def sql
147:       select_sql
148:     end

Returns a TRUNCATE SQL query string. See truncate

  DB[:items].truncate_sql # => 'TRUNCATE items'

[Source]

     # File lib/sequel/dataset/sql.rb, line 153
153:     def truncate_sql
154:       if opts[:sql]
155:         static_sql(opts[:sql])
156:       else
157:         check_truncation_allowed!
158:         raise(InvalidOperation, "Can't truncate filtered datasets") if opts[:where] || opts[:having]
159:         t = String.new
160:         source_list_append(t, opts[:from])
161:         _truncate_sql(t)
162:       end
163:     end

Formats an UPDATE statement using the given values. See update.

  DB[:items].update_sql(:price => 100, :category => 'software')
  # => "UPDATE items SET price = 100, category = 'software'

Raises an Error if the dataset is grouped or includes more than one table.

[Source]

     # File lib/sequel/dataset/sql.rb, line 172
172:     def update_sql(values = OPTS)
173:       return static_sql(opts[:sql]) if opts[:sql]
174:       check_modification_allowed!
175:       clone(:values=>values).send(:_update_sql)
176:     end

9 - Internal Methods relating to SQL Creation

These methods, while public, are not designed to be used directly by the end user.

Classes and Modules

Class Sequel::Dataset::PlaceholderLiteralizer

Constants

EMULATED_FUNCTION_MAP = {}   Map of emulated function names to native function names.
WILDCARD = LiteralString.new('*').freeze
ALL = ' ALL'.freeze
AND_SEPARATOR = " AND ".freeze
APOS = "'".freeze
APOS_RE = /'/.freeze
ARRAY_EMPTY = '(NULL)'.freeze
AS = ' AS '.freeze
ASC = ' ASC'.freeze
BACKSLASH = "\\".freeze
BITCOMP_CLOSE = ") - 1)".freeze
BITCOMP_OPEN = "((0 - ".freeze
BITWISE_METHOD_MAP = {:& =>:BITAND, :| => :BITOR, :^ => :BITXOR}
BOOL_FALSE = "'f'".freeze
BOOL_TRUE = "'t'".freeze
BRACKET_CLOSE = ']'.freeze
BRACKET_OPEN = '['.freeze
CASE_ELSE = " ELSE ".freeze
CASE_END = " END)".freeze
CASE_OPEN = '(CASE'.freeze
CASE_THEN = " THEN ".freeze
CASE_WHEN = " WHEN ".freeze
CAST_OPEN = 'CAST('.freeze
COLON = ':'.freeze
COLUMN_REF_RE1 = Sequel::COLUMN_REF_RE1
COLUMN_REF_RE2 = Sequel::COLUMN_REF_RE2
COLUMN_REF_RE3 = Sequel::COLUMN_REF_RE3
COMMA = ', '.freeze
COMMA_SEPARATOR = COMMA
CONDITION_FALSE = '(1 = 0)'.freeze
CONDITION_TRUE = '(1 = 1)'.freeze
COUNT_FROM_SELF_OPTS = [:distinct, :group, :sql, :limit, :offset, :compounds]
COUNT_OF_ALL_AS_COUNT = SQL::Function.new(:count, WILDCARD).as(:count)
DATASET_ALIAS_BASE_NAME = 't'.freeze
DEFAULT = LiteralString.new('DEFAULT').freeze
DEFAULT_VALUES = " DEFAULT VALUES".freeze
DELETE = 'DELETE'.freeze
DESC = ' DESC'.freeze
DISTINCT = " DISTINCT".freeze
DOT = '.'.freeze
DOUBLE_APOS = "''".freeze
DOUBLE_QUOTE = '""'.freeze
EQUAL = ' = '.freeze
EMPTY_PARENS = '()'.freeze
ESCAPE = " ESCAPE ".freeze
EXTRACT = 'extract('.freeze
EXISTS = ['EXISTS '.freeze].freeze
FILTER = " FILTER (WHERE ".freeze
FOR_UPDATE = ' FOR UPDATE'.freeze
FORMAT_DATE = "'%Y-%m-%d'".freeze
FORMAT_DATE_STANDARD = "DATE '%Y-%m-%d'".freeze
FORMAT_OFFSET = "%+03i%02i".freeze
FORMAT_TIMESTAMP_RE = /%[Nz]/.freeze
FORMAT_USEC = '%N'.freeze
FRAME_ALL = "ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING".freeze
FRAME_ROWS = "ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW".freeze
FROM = ' FROM '.freeze
FUNCTION_DISTINCT = "DISTINCT ".freeze
GROUP_BY = " GROUP BY ".freeze
HAVING = " HAVING ".freeze
INSERT = "INSERT".freeze
INTO = " INTO ".freeze
IS_LITERALS = {nil=>'NULL'.freeze, true=>'TRUE'.freeze, false=>'FALSE'.freeze}.freeze
IS_OPERATORS = ::Sequel::SQL::ComplexExpression::IS_OPERATORS
LATERAL = 'LATERAL '.freeze
LIKE_OPERATORS = ::Sequel::SQL::ComplexExpression::LIKE_OPERATORS
LIMIT = " LIMIT ".freeze
N_ARITY_OPERATORS = ::Sequel::SQL::ComplexExpression::N_ARITY_OPERATORS
NOT_SPACE = 'NOT '.freeze
NULL = "NULL".freeze
NULLS_FIRST = " NULLS FIRST".freeze
NULLS_LAST = " NULLS LAST".freeze
OFFSET = " OFFSET ".freeze
ON = ' ON '.freeze
ON_PAREN = " ON (".freeze
ORDER_BY = " ORDER BY ".freeze
ORDER_BY_NS = "ORDER BY ".freeze
OVER = ' OVER '.freeze
PAREN_CLOSE = ')'.freeze
PAREN_OPEN = '('.freeze
PAREN_SPACE_OPEN = ' ('.freeze
PARTITION_BY = "PARTITION BY ".freeze
QUALIFY_KEYS = [:select, :where, :having, :order, :group]
QUESTION_MARK = '?'.freeze
QUESTION_MARK_RE = /\?/.freeze
QUOTE = '"'.freeze
QUOTE_RE = /"/.freeze
RETURNING = " RETURNING ".freeze
SELECT = 'SELECT'.freeze
SET = ' SET '.freeze
SPACE = ' '.freeze
SQL_WITH = "WITH ".freeze
SPACE_WITH = " WITH ".freeze
TILDE = '~'.freeze
TIMESTAMP_FORMAT = "'%Y-%m-%d %H:%M:%S%N%z'".freeze
STANDARD_TIMESTAMP_FORMAT = "TIMESTAMP #{TIMESTAMP_FORMAT}".freeze
TWO_ARITY_OPERATORS = ::Sequel::SQL::ComplexExpression::TWO_ARITY_OPERATORS
REGEXP_OPERATORS = ::Sequel::SQL::ComplexExpression::REGEXP_OPERATORS
UNDERSCORE = '_'.freeze
UPDATE = 'UPDATE'.freeze
USING = ' USING ('.freeze
UNION_ALL_SELECT = ' UNION ALL SELECT '.freeze
VALUES = " VALUES ".freeze
WHERE = " WHERE ".freeze
WITH_ORDINALITY = " WITH ORDINALITY".freeze
WITHIN_GROUP = " WITHIN GROUP (ORDER BY ".freeze
DATETIME_SECFRACTION_ARG = RUBY_VERSION >= '1.9.0' ? 1000000 : 86400000000

Public Class methods

Given a type (e.g. select) and an array of clauses, return an array of methods to call to build the SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 185
185:     def self.clause_methods(type, clauses)
186:       clauses.map{|clause| "#{type}_#{clause}_sql""#{type}_#{clause}_sql"}.freeze
187:     end

Define a dataset literalization method for the given type in the given module, using the given clauses.

Arguments:

mod :Module in which to define method
type :Type of SQL literalization method to create, either :select, :insert, :update, or :delete
clauses :array of clauses that make up the SQL query for the type. This can either be a single array of symbols/strings, or it can be an array of pairs, with the first element in each pair being an if/elsif/else code fragment, and the second element in each pair being an array of symbol/strings for the appropriate branch.

[Source]

     # File lib/sequel/dataset/sql.rb, line 199
199:     def self.def_sql_method(mod, type, clauses)
200:       priv = type == :update || type == :insert
201: 
202:       lines = []
203:       lines << 'private' if priv
204:       lines << "def #{'_' if priv}#{type}_sql"
205:       lines << 'if sql = opts[:sql]; return static_sql(sql) end' unless priv
206:       lines << 'check_modification_allowed!' if type == :delete
207:       lines << 'sql = @opts[:append_sql] || sql_string_origin'
208: 
209:       if clauses.all?{|c| c.is_a?(Array)}
210:         clauses.each do |i, cs|
211:           lines << i
212:           lines.concat(clause_methods(type, cs).map{|x| "#{x}(sql)"}) 
213:         end 
214:         lines << 'end'
215:       else
216:         lines.concat(clause_methods(type, clauses).map{|x| "#{x}(sql)"})
217:       end
218: 
219:       lines << 'sql'
220:       lines << 'end'
221: 
222:       mod.class_eval lines.join("\n"), __FILE__, __LINE__
223:     end

Public Instance methods

Append literalization of aliased expression to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 353
353:     def aliased_expression_sql_append(sql, ae)
354:       literal_append(sql, ae.expression)
355:       as_sql_append(sql, ae.alias, ae.columns)
356:     end

Append literalization of array to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 359
359:     def array_sql_append(sql, a)
360:       if a.empty?
361:         sql << ARRAY_EMPTY
362:       else
363:         sql << PAREN_OPEN
364:         expression_list_append(sql, a)
365:         sql << PAREN_CLOSE
366:       end
367:     end

Append literalization of boolean constant to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 370
370:     def boolean_constant_sql_append(sql, constant)
371:       if (constant == true || constant == false) && !supports_where_true?
372:         sql << (constant == true ? CONDITION_TRUE : CONDITION_FALSE)
373:       else
374:         literal_append(sql, constant)
375:       end
376:     end

Append literalization of case expression to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 379
379:     def case_expression_sql_append(sql, ce)
380:       sql << CASE_OPEN
381:       if ce.expression?
382:         sql << SPACE
383:         literal_append(sql, ce.expression)
384:       end
385:       w = CASE_WHEN
386:       t = CASE_THEN
387:       ce.conditions.each do |c,r|
388:         sql << w
389:         literal_append(sql, c)
390:         sql << t
391:         literal_append(sql, r)
392:       end
393:       sql << CASE_ELSE
394:       literal_append(sql, ce.default)
395:       sql << CASE_END
396:     end

Append literalization of cast expression to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 399
399:     def cast_sql_append(sql, expr, type)
400:       sql << CAST_OPEN
401:       literal_append(sql, expr)
402:       sql << AS << db.cast_type_literal(type).to_s
403:       sql << PAREN_CLOSE
404:     end

Append literalization of column all selection to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 407
407:     def column_all_sql_append(sql, ca)
408:       qualified_identifier_sql_append(sql, ca.table, WILDCARD)
409:     end

Append literalization of complex expression to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 412
412:     def complex_expression_sql_append(sql, op, args)
413:       case op
414:       when *IS_OPERATORS
415:         r = args.at(1)
416:         if r.nil? || supports_is_true?
417:           raise(InvalidOperation, 'Invalid argument used for IS operator') unless val = IS_LITERALS[r]
418:           sql << PAREN_OPEN
419:           literal_append(sql, args.at(0))
420:           sql << SPACE << op.to_s << SPACE
421:           sql << val << PAREN_CLOSE
422:         elsif op == :IS
423:           complex_expression_sql_append(sql, "=""=", args)
424:         else
425:           complex_expression_sql_append(sql, :OR, [SQL::BooleanExpression.new("!=""!=", *args), SQL::BooleanExpression.new(:IS, args.at(0), nil)])
426:         end
427:       when :IN, "NOT IN""NOT IN"
428:         cols = args.at(0)
429:         vals = args.at(1)
430:         col_array = true if cols.is_a?(Array)
431:         if vals.is_a?(Array)
432:           val_array = true
433:           empty_val_array = vals == []
434:         end
435:         if empty_val_array
436:           literal_append(sql, empty_array_value(op, cols))
437:         elsif col_array
438:           if !supports_multiple_column_in?
439:             if val_array
440:               expr = SQL::BooleanExpression.new(:OR, *vals.to_a.map{|vs| SQL::BooleanExpression.from_value_pairs(cols.to_a.zip(vs).map{|c, v| [c, v]})})
441:               literal_append(sql, op == :IN ? expr : ~expr)
442:             else
443:               old_vals = vals
444:               vals = vals.naked if vals.is_a?(Sequel::Dataset)
445:               vals = vals.to_a
446:               val_cols = old_vals.columns
447:               complex_expression_sql_append(sql, op, [cols, vals.map!{|x| x.values_at(*val_cols)}])
448:             end
449:           else
450:             # If the columns and values are both arrays, use array_sql instead of
451:             # literal so that if values is an array of two element arrays, it
452:             # will be treated as a value list instead of a condition specifier.
453:             sql << PAREN_OPEN
454:             literal_append(sql, cols)
455:             sql << SPACE << op.to_s << SPACE
456:             if val_array
457:               array_sql_append(sql, vals)
458:             else
459:               literal_append(sql, vals)
460:             end
461:             sql << PAREN_CLOSE
462:           end
463:         else
464:           sql << PAREN_OPEN
465:           literal_append(sql, cols)
466:           sql << SPACE << op.to_s << SPACE
467:           literal_append(sql, vals)
468:           sql << PAREN_CLOSE
469:         end
470:       when :LIKE, 'NOT LIKE''NOT LIKE'
471:         sql << PAREN_OPEN
472:         literal_append(sql, args.at(0))
473:         sql << SPACE << op.to_s << SPACE
474:         literal_append(sql, args.at(1))
475:         sql << ESCAPE
476:         literal_append(sql, BACKSLASH)
477:         sql << PAREN_CLOSE
478:       when :ILIKE, 'NOT ILIKE''NOT ILIKE'
479:         complex_expression_sql_append(sql, (op == :ILIKE ? :LIKE : "NOT LIKE""NOT LIKE"), args.map{|v| Sequel.function(:UPPER, v)})
480:       when :**
481:         function_sql_append(sql, Sequel.function(:power, *args))
482:       when *TWO_ARITY_OPERATORS
483:         if REGEXP_OPERATORS.include?(op) && !supports_regexp?
484:           raise InvalidOperation, "Pattern matching via regular expressions is not supported on #{db.database_type}"
485:         end
486:         sql << PAREN_OPEN
487:         literal_append(sql, args.at(0))
488:         sql << SPACE << op.to_s << SPACE
489:         literal_append(sql, args.at(1))
490:         sql << PAREN_CLOSE
491:       when *N_ARITY_OPERATORS
492:         sql << PAREN_OPEN
493:         c = false
494:         op_str = " #{op} "
495:         args.each do |a|
496:           sql << op_str if c
497:           literal_append(sql, a)
498:           c ||= true
499:         end
500:         sql << PAREN_CLOSE
501:       when :NOT
502:         sql << NOT_SPACE
503:         literal_append(sql, args.at(0))
504:       when :NOOP
505:         literal_append(sql, args.at(0))
506:       when 'B~''B~'
507:         sql << TILDE
508:         literal_append(sql, args.at(0))
509:       when :extract
510:         sql << EXTRACT << args.at(0).to_s << FROM
511:         literal_append(sql, args.at(1))
512:         sql << PAREN_CLOSE
513:       else
514:         raise(InvalidOperation, "invalid operator #{op}")
515:       end
516:     end

Append literalization of constant to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 519
519:     def constant_sql_append(sql, constant)
520:       sql << constant.to_s
521:     end

Append literalization of delayed evaluation to SQL string, causing the delayed evaluation proc to be evaluated.

[Source]

     # File lib/sequel/dataset/sql.rb, line 525
525:     def delayed_evaluation_sql_append(sql, delay)
526:       if recorder = @opts[:placeholder_literalizer]
527:         recorder.use(sql, lambda{delay.call(self)}, nil)
528:       else
529:         literal_append(sql, delay.call(self))
530:       end
531:     end

Append literalization of function call to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 534
534:     def function_sql_append(sql, f)
535:       name = f.name
536:       opts = f.opts
537: 
538:       if opts[:emulate]
539:         if emulate_function?(name)
540:           emulate_function_sql_append(sql, f)
541:           return
542:         end
543: 
544:         name = native_function_name(name) 
545:       end
546: 
547:       sql << LATERAL if opts[:lateral]
548: 
549:       case name
550:       when SQL::Identifier
551:         if supports_quoted_function_names? && opts[:quoted] != false
552:           literal_append(sql, name)
553:         else
554:           sql << name.value.to_s
555:         end
556:       when SQL::QualifiedIdentifier
557:         if supports_quoted_function_names? && opts[:quoted] != false
558:           literal_append(sql, name)
559:         else
560:           sql << split_qualifiers(name).join(DOT)
561:         end
562:       else
563:         if supports_quoted_function_names? && opts[:quoted]
564:           quote_identifier_append(sql, name)
565:         else
566:           sql << name.to_s
567:         end
568:       end
569: 
570:       sql << PAREN_OPEN
571:       if opts[:*]
572:         sql << WILDCARD
573:       else
574:         sql << FUNCTION_DISTINCT if opts[:distinct]
575:         expression_list_append(sql, f.args)
576:         if order = opts[:order]
577:           sql << ORDER_BY
578:           expression_list_append(sql, order)
579:         end
580:       end
581:       sql << PAREN_CLOSE
582: 
583:       if group = opts[:within_group]
584:         sql << WITHIN_GROUP
585:         expression_list_append(sql, group)
586:         sql << PAREN_CLOSE
587:       end
588: 
589:       if filter = opts[:filter]
590:         sql << FILTER
591:         literal_append(sql, filter_expr(filter, &opts[:filter_block]))
592:         sql << PAREN_CLOSE
593:       end
594: 
595:       if window = opts[:over]
596:         sql << OVER
597:         window_sql_append(sql, window.opts)
598:       end
599: 
600:       if opts[:with_ordinality]
601:         sql << WITH_ORDINALITY
602:       end
603:     end

Append literalization of JOIN clause without ON or USING to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 606
606:     def join_clause_sql_append(sql, jc)
607:       table = jc.table
608:       table_alias = jc.table_alias
609:       table_alias = nil if table == table_alias && !jc.column_aliases
610:       sql << SPACE << join_type_sql(jc.join_type) << SPACE
611:       identifier_append(sql, table)
612:       as_sql_append(sql, table_alias, jc.column_aliases) if table_alias
613:     end

Append literalization of JOIN ON clause to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 616
616:     def join_on_clause_sql_append(sql, jc)
617:       join_clause_sql_append(sql, jc)
618:       sql << ON
619:       literal_append(sql, filter_expr(jc.on))
620:     end

Append literalization of JOIN USING clause to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 623
623:     def join_using_clause_sql_append(sql, jc)
624:       join_clause_sql_append(sql, jc)
625:       sql << USING
626:       column_list_append(sql, jc.using)
627:       sql << PAREN_CLOSE
628:     end

Append literalization of negative boolean constant to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 631
631:     def negative_boolean_constant_sql_append(sql, constant)
632:       sql << NOT_SPACE
633:       boolean_constant_sql_append(sql, constant)
634:     end

Append literalization of ordered expression to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 637
637:     def ordered_expression_sql_append(sql, oe)
638:       literal_append(sql, oe.expression)
639:       sql << (oe.descending ? DESC : ASC)
640:       case oe.nulls
641:       when :first
642:         sql << NULLS_FIRST
643:       when :last
644:         sql << NULLS_LAST
645:       end
646:     end

Append literalization of placeholder literal string to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 649
649:     def placeholder_literal_string_sql_append(sql, pls)
650:       args = pls.args
651:       str = pls.str
652:       sql << PAREN_OPEN if pls.parens
653:       if args.is_a?(Hash)
654:         if args.empty?
655:           sql << str
656:         else
657:           re = /:(#{args.keys.map{|k| Regexp.escape(k.to_s)}.join('|')})\b/
658:           loop do
659:             previous, q, str = str.partition(re)
660:             sql << previous
661:             literal_append(sql, args[($1||q[1..-1].to_s).to_sym]) unless q.empty?
662:             break if str.empty?
663:           end
664:         end
665:       elsif str.is_a?(Array)
666:         len = args.length
667:         str.each_with_index do |s, i|
668:           sql << s
669:           literal_append(sql, args[i]) unless i == len
670:         end
671:         unless str.length == args.length || str.length == args.length + 1
672:           raise Error, "Mismatched number of placeholders (#{str.length}) and placeholder arguments (#{args.length}) when using placeholder array"
673:         end
674:       else
675:         i = -1
676:         match_len = args.length - 1
677:         loop do
678:           previous, q, str = str.partition(QUESTION_MARK)
679:           sql << previous
680:           literal_append(sql, args.at(i+=1)) unless q.empty?
681:           if str.empty?
682:             unless i == match_len
683:               raise Error, "Mismatched number of placeholders (#{i+1}) and placeholder arguments (#{args.length}) when using placeholder array"
684:             end
685:             break
686:           end
687:         end
688:       end
689:       sql << PAREN_CLOSE if pls.parens
690:     end

Append literalization of qualified identifier to SQL string. If 3 arguments are given, the 2nd should be the table/qualifier and the third should be column/qualified. If 2 arguments are given, the 2nd should be an SQL::QualifiedIdentifier.

[Source]

     # File lib/sequel/dataset/sql.rb, line 695
695:     def qualified_identifier_sql_append(sql, table, column=(c = table.column; table = table.table; c))
696:       identifier_append(sql, table)
697:       sql << DOT
698:       identifier_append(sql, column)
699:     end

Append literalization of unqualified identifier to SQL string. Adds quoting to identifiers (columns and tables). If identifiers are not being quoted, returns name as a string. If identifiers are being quoted quote the name with quoted_identifier.

[Source]

     # File lib/sequel/dataset/sql.rb, line 705
705:     def quote_identifier_append(sql, name)
706:       if name.is_a?(LiteralString)
707:         sql << name
708:       else
709:         name = name.value if name.is_a?(SQL::Identifier)
710:         name = input_identifier(name)
711:         if quote_identifiers?
712:           quoted_identifier_append(sql, name)
713:         else
714:           sql << name
715:         end
716:       end
717:     end

Append literalization of identifier or unqualified identifier to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 720
720:     def quote_schema_table_append(sql, table)
721:       schema, table = schema_and_table(table)
722:       if schema
723:         quote_identifier_append(sql, schema)
724:         sql << DOT
725:       end
726:       quote_identifier_append(sql, table)
727:     end

Append literalization of quoted identifier to SQL string. This method quotes the given name with the SQL standard double quote. should be overridden by subclasses to provide quoting not matching the SQL standard, such as backtick (used by MySQL and SQLite).

[Source]

     # File lib/sequel/dataset/sql.rb, line 733
733:     def quoted_identifier_append(sql, name)
734:       sql << QUOTE << name.to_s.gsub(QUOTE_RE, DOUBLE_QUOTE) << QUOTE
735:     end

Split the schema information from the table, returning two strings, one for the schema and one for the table. The returned schema may be nil, but the table will always have a string value.

Note that this function does not handle tables with more than one level of qualification (e.g. database.schema.table on Microsoft SQL Server).

[Source]

     # File lib/sequel/dataset/sql.rb, line 744
744:     def schema_and_table(table_name, sch=nil)
745:       sch = sch.to_s if sch
746:       case table_name
747:       when Symbol
748:         s, t, _ = split_symbol(table_name)
749:         [s||sch, t]
750:       when SQL::QualifiedIdentifier
751:         [table_name.table.to_s, table_name.column.to_s]
752:       when SQL::Identifier
753:         [sch, table_name.value.to_s]
754:       when String
755:         [sch, table_name]
756:       else
757:         raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
758:       end
759:     end

Splits table_name into an array of strings.

  ds.split_qualifiers(:s) # ['s']
  ds.split_qualifiers(:t__s) # ['t', 's']
  ds.split_qualifiers(Sequel.qualify(:d, :t__s)) # ['d', 't', 's']
  ds.split_qualifiers(Sequel.qualify(:h__d, :t__s)) # ['h', 'd', 't', 's']

[Source]

     # File lib/sequel/dataset/sql.rb, line 767
767:     def split_qualifiers(table_name, *args)
768:       case table_name
769:       when SQL::QualifiedIdentifier
770:         split_qualifiers(table_name.table, nil) + split_qualifiers(table_name.column, nil)
771:       else
772:         sch, table = schema_and_table(table_name, *args)
773:         sch ? [sch, table] : [table]
774:       end
775:     end

Append literalization of subscripts (SQL array accesses) to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 778
778:     def subscript_sql_append(sql, s)
779:       literal_append(sql, s.f)
780:       sql << BRACKET_OPEN
781:       if s.sub.length == 1 && (range = s.sub.first).is_a?(Range)
782:         literal_append(sql, range.begin)
783:         sql << COLON
784:         e = range.end
785:         e -= 1 if range.exclude_end? && e.is_a?(Integer)
786:         literal_append(sql, e)
787:       else
788:         expression_list_append(sql, s.sub)
789:       end
790:       sql << BRACKET_CLOSE
791:     end

Append literalization of windows (for window functions) to SQL string.

[Source]

     # File lib/sequel/dataset/sql.rb, line 794
794:     def window_sql_append(sql, opts)
795:       raise(Error, 'This dataset does not support window functions') unless supports_window_functions?
796:       sql << PAREN_OPEN
797:       window, part, order, frame = opts.values_at(:window, :partition, :order, :frame)
798:       space = false
799:       space_s = SPACE
800:       if window
801:         literal_append(sql, window)
802:         space = true
803:       end
804:       if part
805:         sql << space_s if space
806:         sql << PARTITION_BY
807:         expression_list_append(sql, Array(part))
808:         space = true
809:       end
810:       if order
811:         sql << space_s if space
812:         sql << ORDER_BY_NS
813:         expression_list_append(sql, Array(order))
814:         space = true
815:       end
816:       case frame
817:         when nil
818:           # nothing
819:         when :all
820:           sql << space_s if space
821:           sql << FRAME_ALL
822:         when :rows
823:           sql << space_s if space
824:           sql << FRAME_ROWS
825:         when String
826:           sql << space_s if space
827:           sql << frame
828:         else
829:           raise Error, "invalid window frame clause, should be :all, :rows, a string, or nil"
830:       end
831:       sql << PAREN_CLOSE
832:     end

Protected Instance methods

Return a from_self dataset if an order or limit is specified, so it works as expected with UNION, EXCEPT, and INTERSECT clauses.

[Source]

     # File lib/sequel/dataset/sql.rb, line 838
838:     def compound_from_self
839:       (@opts[:sql] || @opts[:limit] || @opts[:order]) ? from_self : self
840:     end

8 - Methods related to prepared statements or bound variables

On some adapters, these use native prepared statements and bound variables, on others support is emulated. For details, see the "Prepared Statements/Bound Variables" guide.

Constants

PREPARED_ARG_PLACEHOLDER = LiteralString.new('?').freeze
DEFAULT_PREPARED_STATEMENT_MODULE_METHODS = %w'execute execute_dui execute_insert'.freeze.each(&:freeze)
PREPARED_STATEMENT_MODULE_CODE = { :bind => "opts = Hash[opts]; opts[:arguments] = bind_arguments".freeze, :prepare => "sql = prepared_statement_name".freeze, :prepare_bind => "sql = prepared_statement_name; opts = Hash[opts]; opts[:arguments] = bind_arguments".freeze

Public Instance methods

Set the bind variables to use for the call. If bind variables have already been set for this dataset, they are updated with the contents of bind_vars.

  DB[:table].filter(:id=>:$id).bind(:id=>1).call(:first)
  # SELECT * FROM table WHERE id = ? LIMIT 1 -- (1)
  # => {:id=>1}

[Source]

     # File lib/sequel/dataset/prepared_statements.rb, line 261
261:     def bind(bind_vars={})
262:       clone(:bind_vars=>@opts[:bind_vars] ? Hash[@opts[:bind_vars]].merge!(bind_vars) : bind_vars)
263:     end

For the given type (:select, :first, :insert, :insert_select, :update, or :delete), run the sql with the bind variables specified in the hash. values is a hash passed to insert or update (if one of those types is used), which may contain placeholders.

  DB[:table].filter(:id=>:$id).call(:first, :id=>1)
  # SELECT * FROM table WHERE id = ? LIMIT 1 -- (1)
  # => {:id=>1}

[Source]

     # File lib/sequel/dataset/prepared_statements.rb, line 272
272:     def call(type, bind_variables={}, *values, &block)
273:       prepare(type, nil, *values).call(bind_variables, &block)
274:     end

Prepare an SQL statement for later execution. Takes a type similar to call, and the name symbol of the prepared statement. While name defaults to nil, it should always be provided as a symbol for the name of the prepared statement, as some databases require that prepared statements have names.

This returns a clone of the dataset extended with PreparedStatementMethods, which you can call with the hash of bind variables to use. The prepared statement is also stored in the associated database, where it can be called by name. The following usage is identical:

  ps = DB[:table].filter(:name=>:$name).prepare(:first, :select_by_name)

  ps.call(:name=>'Blah')
  # SELECT * FROM table WHERE name = ? -- ('Blah')
  # => {:id=>1, :name=>'Blah'}

  DB.call(:select_by_name, :name=>'Blah') # Same thing

[Source]

     # File lib/sequel/dataset/prepared_statements.rb, line 294
294:     def prepare(type, name=nil, *values)
295:       ps = to_prepared_statement(type, values)
296:       db.set_prepared_statement(name, ps) if name
297:       ps
298:     end

Protected Instance methods

Return a cloned copy of the current dataset extended with PreparedStatementMethods, setting the type and modify values.

[Source]

     # File lib/sequel/dataset/prepared_statements.rb, line 304
304:     def to_prepared_statement(type, values=nil)
305:       ps = bind
306:       ps.extend(PreparedStatementMethods)
307:       ps.orig_dataset = self
308:       ps.prepared_type = type
309:       ps.prepared_modify_values = values
310:       ps
311:     end

5 - Methods related to dataset graphing

Dataset graphing automatically creates unique aliases columns in join tables that overlap with already selected column aliases. All of these methods return modified copies of the receiver.

Public Instance methods

Adds the given graph aliases to the list of graph aliases to use, unlike set_graph_aliases, which replaces the list (the equivalent of select_more when graphing). See set_graph_aliases.

  DB[:table].add_graph_aliases(:some_alias=>[:table, :column])
  # SELECT ..., table.column AS some_alias

[Source]

    # File lib/sequel/dataset/graph.rb, line 18
18:     def add_graph_aliases(graph_aliases)
19:       unless (ga = opts[:graph_aliases]) || (opts[:graph] && (ga = opts[:graph][:column_aliases]))
20:         raise Error, "cannot call add_graph_aliases on a dataset that has not been called with graph or set_graph_aliases"
21:       end
22:       columns, graph_aliases = graph_alias_columns(graph_aliases)
23:       select_more(*columns).clone(:graph_aliases => Hash[ga].merge!(graph_aliases))
24:     end

Similar to Dataset#join_table, but uses unambiguous aliases for selected columns and keeps metadata about the aliases for use in other methods.

Arguments:

dataset :Can be a symbol (specifying a table), another dataset, or an SQL::Identifier, SQL::QualifiedIdentifier, or SQL::AliasedExpression.
join_conditions :Any condition(s) allowed by join_table.
block :A block that is passed to join_table.

Options:

:from_self_alias :The alias to use when the receiver is not a graphed dataset but it contains multiple FROM tables or a JOIN. In this case, the receiver is wrapped in a from_self before graphing, and this option determines the alias to use.
:implicit_qualifier :The qualifier of implicit conditions, see join_table.
:join_only :Only join the tables, do not change the selected columns.
:join_type :The type of join to use (passed to join_table). Defaults to :left_outer.
:qualify:The type of qualification to do, see join_table.
:select :An array of columns to select. When not used, selects all columns in the given dataset. When set to false, selects no columns and is like simply joining the tables, though graph keeps some metadata about the join that makes it important to use graph instead of join_table.
:table_alias :The alias to use for the table. If not specified, doesn‘t alias the table. You will get an error if the alias (or table) name is used more than once.

[Source]

     # File lib/sequel/dataset/graph.rb, line 52
 52:     def graph(dataset, join_conditions = nil, options = OPTS, &block)
 53:       # Allow the use of a dataset or symbol as the first argument
 54:       # Find the table name/dataset based on the argument
 55:       table_alias = options[:table_alias]
 56:       table = dataset
 57:       create_dataset = true
 58: 
 59:       case dataset
 60:       when Symbol
 61:         # let alias be the same as the table name (sans any optional schema)
 62:         # unless alias explicitly given in the symbol using ___ notation
 63:         table_alias ||= split_symbol(table).compact.last
 64:       when Dataset
 65:         if dataset.simple_select_all?
 66:           table = dataset.opts[:from].first
 67:           table_alias ||= table
 68:         else
 69:           table_alias ||= dataset_alias((@opts[:num_dataset_sources] || 0)+1)
 70:         end
 71:         create_dataset = false
 72:       when SQL::Identifier
 73:         table_alias ||= table.value
 74:       when SQL::QualifiedIdentifier
 75:         table_alias ||= split_qualifiers(table).last
 76:       when SQL::AliasedExpression
 77:         return graph(table.expression, join_conditions, {:table_alias=>table.alias}.merge!(options), &block)
 78:       else
 79:         raise Error, "The dataset argument should be a symbol or dataset"
 80:       end
 81:       table_alias = table_alias.to_sym
 82: 
 83:       if create_dataset
 84:         dataset = db.from(table)
 85:       end
 86: 
 87:       # Raise Sequel::Error with explanation that the table alias has been used
 88:       raise_alias_error = lambda do
 89:         raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
 90:           "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}") 
 91:       end
 92: 
 93:       # Only allow table aliases that haven't been used
 94:       raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
 95:       
 96:       table_alias_qualifier = qualifier_from_alias_symbol(table_alias, table)
 97:       implicit_qualifier = options[:implicit_qualifier]
 98:       ds = self
 99: 
100:       # Use a from_self if this is already a joined table (or from_self specifically disabled for graphs)
101:       if (@opts[:graph_from_self] != false && !@opts[:graph] && joined_dataset?)
102:         from_selfed = true
103:         implicit_qualifier = options[:from_self_alias] || first_source
104:         ds = ds.from_self(:alias=>implicit_qualifier)
105:       end
106:       
107:       # Join the table early in order to avoid cloning the dataset twice
108:       ds = ds.join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias_qualifier, :implicit_qualifier=>implicit_qualifier, :qualify=>options[:qualify], &block)
109: 
110:       return ds if options[:join_only]
111: 
112:       opts = ds.opts
113: 
114:       # Whether to include the table in the result set
115:       add_table = options[:select] == false ? false : true
116:       # Whether to add the columns to the list of column aliases
117:       add_columns = !ds.opts.include?(:graph_aliases)
118: 
119:       if graph = opts[:graph]
120:         opts[:graph] = graph = graph.dup
121:         select = opts[:select].dup
122:         [:column_aliases, :table_aliases, :column_alias_num].each{|k| graph[k] = graph[k].dup}
123:       else
124:         # Setup the initial graph data structure if it doesn't exist
125:         qualifier = ds.first_source_alias
126:         master = alias_symbol(qualifier)
127:         raise_alias_error.call if master == table_alias
128: 
129:         # Master hash storing all .graph related information
130:         graph = opts[:graph] = {}
131: 
132:         # Associates column aliases back to tables and columns
133:         column_aliases = graph[:column_aliases] = {}
134: 
135:         # Associates table alias (the master is never aliased)
136:         table_aliases = graph[:table_aliases] = {master=>self}
137: 
138:         # Keep track of the alias numbers used
139:         ca_num = graph[:column_alias_num] = Hash.new(0)
140: 
141:         # All columns in the master table are never
142:         # aliased, but are not included if set_graph_aliases
143:         # has been used.
144:         if add_columns
145:           if (select = @opts[:select]) && !select.empty? && !(select.length == 1 && (select.first.is_a?(SQL::ColumnAll)))
146:             select = select.map do |sel|
147:               raise Error, "can't figure out alias to use for graphing for #{sel.inspect}" unless column = _hash_key_symbol(sel)
148:               column_aliases[column] = [master, column]
149:               if from_selfed
150:                 # Initial dataset was wrapped in subselect, selected all
151:                 # columns in the subselect, qualified by the subselect alias.
152:                 Sequel.qualify(qualifier, Sequel.identifier(column))
153:               else
154:                 # Initial dataset not wrapped in subslect, just make
155:                 # sure columns are qualified in some way.
156:                 qualified_expression(sel, qualifier)
157:               end
158:             end
159:           else
160:             select = columns.map do |column|
161:               column_aliases[column] = [master, column]
162:               SQL::QualifiedIdentifier.new(qualifier, column)
163:             end
164:           end
165:         end
166:       end
167: 
168:       # Add the table alias to the list of aliases
169:       # Even if it isn't been used in the result set,
170:       # we add a key for it with a nil value so we can check if it
171:       # is used more than once
172:       table_aliases = graph[:table_aliases]
173:       table_aliases[table_alias] = add_table ? dataset : nil
174: 
175:       # Add the columns to the selection unless we are ignoring them
176:       if add_table && add_columns
177:         column_aliases = graph[:column_aliases]
178:         ca_num = graph[:column_alias_num]
179:         # Which columns to add to the result set
180:         cols = options[:select] || dataset.columns
181:         # If the column hasn't been used yet, don't alias it.
182:         # If it has been used, try table_column.
183:         # If that has been used, try table_column_N 
184:         # using the next value of N that we know hasn't been
185:         # used
186:         cols.each do |column|
187:           col_alias, identifier = if column_aliases[column]
188:             column_alias = "#{table_alias}_#{column}""#{table_alias}_#{column}"
189:             if column_aliases[column_alias]
190:               column_alias_num = ca_num[column_alias]
191:               column_alias = "#{column_alias}_#{column_alias_num}""#{column_alias}_#{column_alias_num}" 
192:               ca_num[column_alias] += 1
193:             end
194:             [column_alias, SQL::AliasedExpression.new(SQL::QualifiedIdentifier.new(table_alias_qualifier, column), column_alias)]
195:           else
196:             ident = SQL::QualifiedIdentifier.new(table_alias_qualifier, column)
197:             [column, ident]
198:           end
199:           column_aliases[col_alias] = [table_alias, column]
200:           select.push(identifier)
201:         end
202:       end
203:       add_columns ? ds.select(*select) : ds
204:     end

This allows you to manually specify the graph aliases to use when using graph. You can use it to only select certain columns, and have those columns mapped to specific aliases in the result set. This is the equivalent of select for a graphed dataset, and must be used instead of select whenever graphing is used.

graph_aliases :Should be a hash with keys being symbols of column aliases, and values being either symbols or arrays with one to three elements. If the value is a symbol, it is assumed to be the same as a one element array containing that symbol. The first element of the array should be the table alias symbol. The second should be the actual column name symbol. If the array only has a single element the column name symbol will be assumed to be the same as the corresponding hash key. If the array has a third element, it is used as the value returned, instead of table_alias.column_name.
  DB[:artists].graph(:albums, :artist_id=>:id).
    set_graph_aliases(:name=>:artists,
                      :album_name=>[:albums, :name],
                      :forty_two=>[:albums, :fourtwo, 42]).first
  # SELECT artists.name, albums.name AS album_name, 42 AS forty_two ...

[Source]

     # File lib/sequel/dataset/graph.rb, line 229
229:     def set_graph_aliases(graph_aliases)
230:       columns, graph_aliases = graph_alias_columns(graph_aliases)
231:       ds = select(*columns)
232:       ds.opts[:graph_aliases] = graph_aliases
233:       ds
234:     end

Remove the splitting of results into subhashes, and all metadata related to the current graph (if any).

[Source]

     # File lib/sequel/dataset/graph.rb, line 238
238:     def ungraphed
239:       clone(:graph=>nil, :graph_aliases=>nil)
240:     end

2 - Methods that execute code on the database

These methods all execute the dataset‘s SQL on the database. They don‘t return modified datasets, so if used in a method chain they should be the last method called.

Constants

ACTION_METHODS = (<<-METHS).split.map(&:to_sym) << [] all avg count columns columns! delete each empty? fetch_rows first first! get import insert interval last map max min multi_insert paged_each range select_hash select_hash_groups select_map select_order_map single_record single_record! single_value single_value! sum to_hash to_hash_groups truncate update METHS ).split.map(&:to_sym)   Action methods defined by Sequel that execute code on the database.

Public Instance methods

Inserts the given argument into the database. Returns self so it can be used safely when chaining:

  DB[:items] << {:id=>0, :name=>'Zero'} << DB[:old_items].select(:id, name)

[Source]

    # File lib/sequel/dataset/actions.rb, line 25
25:     def <<(arg)
26:       insert(arg)
27:       self
28:     end

Returns the first record matching the conditions. Examples:

  DB[:table][:id=>1] # SELECT * FROM table WHERE (id = 1) LIMIT 1
  # => {:id=1}

[Source]

    # File lib/sequel/dataset/actions.rb, line 34
34:     def [](*conditions)
35:       raise(Error, ARRAY_ACCESS_ERROR_MSG) if (conditions.length == 1 and conditions.first.is_a?(Integer)) or conditions.length == 0
36:       first(*conditions)
37:     end

Returns an array with all records in the dataset. If a block is given, the array is iterated over after all items have been loaded.

  DB[:table].all # SELECT * FROM table
  # => [{:id=>1, ...}, {:id=>2, ...}, ...]

  # Iterate over all rows in the table
  DB[:table].all{|row| p row}

[Source]

    # File lib/sequel/dataset/actions.rb, line 47
47:     def all(&block)
48:       _all(block){|a| each{|r| a << r}}
49:     end

Returns the average value for the given column/expression. Uses a virtual row block if no argument is given.

  DB[:table].avg(:number) # SELECT avg(number) FROM table LIMIT 1
  # => 3
  DB[:table].avg{function(column)} # SELECT avg(function(column)) FROM table LIMIT 1
  # => 1

[Source]

    # File lib/sequel/dataset/actions.rb, line 58
58:     def avg(column=Sequel.virtual_row(&Proc.new))
59:       aggregate_dataset.get{avg(column).as(:avg)}
60:     end

Returns the columns in the result set in order as an array of symbols. If the columns are currently cached, returns the cached value. Otherwise, a SELECT query is performed to retrieve a single row in order to get the columns.

If you are looking for all columns for a single table and maybe some information about each column (e.g. database type), see Database#schema.

  DB[:table].columns
  # => [:id, :name]

[Source]

    # File lib/sequel/dataset/actions.rb, line 71
71:     def columns
72:       return @columns if @columns
73:       ds = unfiltered.unordered.naked.clone(:distinct => nil, :limit => 1, :offset=>nil)
74:       ds.each{break}
75:       @columns = ds.instance_variable_get(:@columns)
76:       @columns || []
77:     end

Ignore any cached column information and perform a query to retrieve a row in order to get the columns.

  DB[:table].columns!
  # => [:id, :name]

[Source]

    # File lib/sequel/dataset/actions.rb, line 84
84:     def columns!
85:       self.columns = nil
86:       columns
87:     end

Returns the number of records in the dataset. If an argument is provided, it is used as the argument to count. If a block is provided, it is treated as a virtual row, and the result is used as the argument to count.

  DB[:table].count # SELECT count(*) AS count FROM table LIMIT 1
  # => 3
  DB[:table].count(:column) # SELECT count(column) AS count FROM table LIMIT 1
  # => 2
  DB[:table].count{foo(column)} # SELECT count(foo(column)) AS count FROM table LIMIT 1
  # => 1

[Source]

     # File lib/sequel/dataset/actions.rb, line 100
100:     def count(arg=(no_arg=true), &block)
101:       if no_arg
102:         if block
103:           arg = Sequel.virtual_row(&block)
104:           aggregate_dataset.get{count(arg).as(:count)}
105:         else
106:           aggregate_dataset.get{count{}.*.as(:count)}.to_i
107:         end
108:       elsif block
109:         raise Error, 'cannot provide both argument and block to Dataset#count'
110:       else
111:         aggregate_dataset.get{count(arg).as(:count)}
112:       end
113:     end

Deletes the records in the dataset. The returned value should be number of records deleted, but that is adapter dependent.

  DB[:table].delete # DELETE * FROM table
  # => 3

[Source]

     # File lib/sequel/dataset/actions.rb, line 120
120:     def delete(&block)
121:       sql = delete_sql
122:       if uses_returning?(:delete)
123:         returning_fetch_rows(sql, &block)
124:       else
125:         execute_dui(sql)
126:       end
127:     end

Iterates over the records in the dataset as they are yielded from the database adapter, and returns self.

  DB[:table].each{|row| p row} # SELECT * FROM table

Note that this method is not safe to use on many adapters if you are running additional queries inside the provided block. If you are running queries inside the block, you should use all instead of each for the outer queries, or use a separate thread or shard inside each.

[Source]

     # File lib/sequel/dataset/actions.rb, line 138
138:     def each
139:       if row_proc = @row_proc
140:         fetch_rows(select_sql){|r| yield row_proc.call(r)}
141:       else
142:         fetch_rows(select_sql){|r| yield r}
143:       end
144:       self
145:     end

Returns true if no records exist in the dataset, false otherwise

  DB[:table].empty? # SELECT 1 AS one FROM table LIMIT 1
  # => false

[Source]

     # File lib/sequel/dataset/actions.rb, line 151
151:     def empty?
152:       ds = @opts[:order] ? unordered : self
153:       ds.get(Sequel::SQL::AliasedExpression.new(1, :one)).nil?
154:     end

If a integer argument is given, it is interpreted as a limit, and then returns all matching records up to that limit. If no argument is passed, it returns the first matching record. If any other type of argument(s) is passed, it is given to filter and the first matching record is returned. If a block is given, it is used to filter the dataset before returning anything.

If there are no records in the dataset, returns nil (or an empty array if an integer argument is given).

Examples:

  DB[:table].first # SELECT * FROM table LIMIT 1
  # => {:id=>7}

  DB[:table].first(2) # SELECT * FROM table LIMIT 2
  # => [{:id=>6}, {:id=>4}]

  DB[:table].first(:id=>2) # SELECT * FROM table WHERE (id = 2) LIMIT 1
  # => {:id=>2}

  DB[:table].first("id = 3") # SELECT * FROM table WHERE (id = 3) LIMIT 1
  # => {:id=>3}

  DB[:table].first("id = ?", 4) # SELECT * FROM table WHERE (id = 4) LIMIT 1
  # => {:id=>4}

  DB[:table].first{id > 2} # SELECT * FROM table WHERE (id > 2) LIMIT 1
  # => {:id=>5}

  DB[:table].first("id > ?", 4){id < 6} # SELECT * FROM table WHERE ((id > 4) AND (id < 6)) LIMIT 1
  # => {:id=>5}

  DB[:table].first(2){id < 2} # SELECT * FROM table WHERE (id < 2) LIMIT 2
  # => [{:id=>1}]

[Source]

     # File lib/sequel/dataset/actions.rb, line 191
191:     def first(*args, &block)
192:       ds = block ? filter(&block) : self
193: 
194:       if args.empty?
195:         ds.single_record
196:       else
197:         args = (args.size == 1) ? args.first : args
198:         if args.is_a?(Integer)
199:           ds.limit(args).all
200:         else
201:           ds.filter(args).single_record
202:         end
203:       end
204:     end

Calls first. If first returns nil (signaling that no row matches), raise a Sequel::NoMatchingRow exception.

[Source]

     # File lib/sequel/dataset/actions.rb, line 208
208:     def first!(*args, &block)
209:       first(*args, &block) || raise(Sequel::NoMatchingRow.new(self))
210:     end

Return the column value for the first matching record in the dataset. Raises an error if both an argument and block is given.

  DB[:table].get(:id) # SELECT id FROM table LIMIT 1
  # => 3

  ds.get{sum(id)} # SELECT sum(id) AS v FROM table LIMIT 1
  # => 6

You can pass an array of arguments to return multiple arguments, but you must make sure each element in the array has an alias that Sequel can determine:

  DB[:table].get([:id, :name]) # SELECT id, name FROM table LIMIT 1
  # => [3, 'foo']

  DB[:table].get{[sum(id).as(sum), name]} # SELECT sum(id) AS sum, name FROM table LIMIT 1
  # => [6, 'foo']

[Source]

     # File lib/sequel/dataset/actions.rb, line 230
230:     def get(column=(no_arg=true; nil), &block)
231:       ds = naked
232:       if block
233:         raise(Error, ARG_BLOCK_ERROR_MSG) unless no_arg
234:         ds = ds.select(&block)
235:         column = ds.opts[:select]
236:         column = nil if column.is_a?(Array) && column.length < 2
237:       else
238:         ds = if column.is_a?(Array)
239:           ds.select(*column)
240:         else
241:           ds.select(auto_alias_expression(column))
242:         end
243:       end
244: 
245:       if column.is_a?(Array)
246:        if r = ds.single_record
247:          r.values_at(*hash_key_symbols(column))
248:        end
249:       else
250:         ds.single_value
251:       end
252:     end

Inserts multiple records into the associated table. This method can be used to efficiently insert a large number of records into a table in a single query if the database supports it. Inserts are automatically wrapped in a transaction.

This method is called with a columns array and an array of value arrays:

  DB[:table].import([:x, :y], [[1, 2], [3, 4]])
  # INSERT INTO table (x, y) VALUES (1, 2)
  # INSERT INTO table (x, y) VALUES (3, 4)

This method also accepts a dataset instead of an array of value arrays:

  DB[:table].import([:x, :y], DB[:table2].select(:a, :b))
  # INSERT INTO table (x, y) SELECT a, b FROM table2

Options:

:commit_every :Open a new transaction for every given number of records. For example, if you provide a value of 50, will commit after every 50 records.
:return :When this is set to :primary_key, returns an array of autoincremented primary key values for the rows inserted.
:server :Set the server/shard to use for the transaction and insert queries.
:slice :Same as :commit_every, :commit_every takes precedence.

[Source]

     # File lib/sequel/dataset/actions.rb, line 279
279:     def import(columns, values, opts=OPTS)
280:       return @db.transaction{insert(columns, values)} if values.is_a?(Dataset)
281: 
282:       return if values.empty?
283:       raise(Error, IMPORT_ERROR_MSG) if columns.empty?
284:       ds = opts[:server] ? server(opts[:server]) : self
285:       
286:       if slice_size = opts.fetch(:commit_every, opts.fetch(:slice, default_import_slice))
287:         offset = 0
288:         rows = []
289:         while offset < values.length
290:           rows << ds._import(columns, values[offset, slice_size], opts)
291:           offset += slice_size
292:         end
293:         rows.flatten
294:       else
295:         ds._import(columns, values, opts)
296:       end
297:     end

Inserts values into the associated table. The returned value is generally the value of the primary key for the inserted row, but that is adapter dependent.

insert handles a number of different argument formats:

no arguments or single empty hash :Uses DEFAULT VALUES
single hash :Most common format, treats keys as columns and values as values
single array :Treats entries as values, with no columns
two arrays :Treats first array as columns, second array as values
single Dataset :Treats as an insert based on a selection from the dataset given, with no columns
array and dataset :Treats as an insert based on a selection from the dataset given, with the columns given by the array.

Examples:

  DB[:items].insert
  # INSERT INTO items DEFAULT VALUES

  DB[:items].insert({})
  # INSERT INTO items DEFAULT VALUES

  DB[:items].insert([1,2,3])
  # INSERT INTO items VALUES (1, 2, 3)

  DB[:items].insert([:a, :b], [1,2])
  # INSERT INTO items (a, b) VALUES (1, 2)

  DB[:items].insert(:a => 1, :b => 2)
  # INSERT INTO items (a, b) VALUES (1, 2)

  DB[:items].insert(DB[:old_items])
  # INSERT INTO items SELECT * FROM old_items

  DB[:items].insert([:a, :b], DB[:old_items])
  # INSERT INTO items (a, b) SELECT * FROM old_items

[Source]

     # File lib/sequel/dataset/actions.rb, line 334
334:     def insert(*values, &block)
335:       sql = insert_sql(*values)
336:       if uses_returning?(:insert)
337:         returning_fetch_rows(sql, &block)
338:       else
339:         execute_insert(sql)
340:       end
341:     end

Returns the interval between minimum and maximum values for the given column/expression. Uses a virtual row block if no argument is given.

  DB[:table].interval(:id) # SELECT (max(id) - min(id)) FROM table LIMIT 1
  # => 6
  DB[:table].interval{function(column)} # SELECT (max(function(column)) - min(function(column))) FROM table LIMIT 1
  # => 7

[Source]

     # File lib/sequel/dataset/actions.rb, line 350
350:     def interval(column=Sequel.virtual_row(&Proc.new))
351:       aggregate_dataset.get{(max(column) - min(column)).as(:interval)}
352:     end

Reverses the order and then runs first with the given arguments and block. Note that this will not necessarily give you the last record in the dataset, unless you have an unambiguous order. If there is not currently an order for this dataset, raises an Error.

  DB[:table].order(:id).last # SELECT * FROM table ORDER BY id DESC LIMIT 1
  # => {:id=>10}

  DB[:table].order(Sequel.desc(:id)).last(2) # SELECT * FROM table ORDER BY id ASC LIMIT 2
  # => [{:id=>1}, {:id=>2}]

[Source]

     # File lib/sequel/dataset/actions.rb, line 364
364:     def last(*args, &block)
365:       raise(Error, 'No order specified') unless @opts[:order]
366:       reverse.first(*args, &block)
367:     end

Maps column values for each record in the dataset (if a column name is given), or performs the stock mapping functionality of Enumerable otherwise. Raises an Error if both an argument and block are given.

  DB[:table].map(:id) # SELECT * FROM table
  # => [1, 2, 3, ...]

  DB[:table].map{|r| r[:id] * 2} # SELECT * FROM table
  # => [2, 4, 6, ...]

You can also provide an array of column names:

  DB[:table].map([:id, :name]) # SELECT * FROM table
  # => [[1, 'A'], [2, 'B'], [3, 'C'], ...]

[Source]

     # File lib/sequel/dataset/actions.rb, line 383
383:     def map(column=nil, &block)
384:       if column
385:         raise(Error, ARG_BLOCK_ERROR_MSG) if block
386:         return naked.map(column) if row_proc
387:         if column.is_a?(Array)
388:           super(){|r| r.values_at(*column)}
389:         else
390:           super(){|r| r[column]}
391:         end
392:       else
393:         super(&block)
394:       end
395:     end

Returns the maximum value for the given column/expression. Uses a virtual row block if no argument is given.

  DB[:table].max(:id) # SELECT max(id) FROM table LIMIT 1
  # => 10
  DB[:table].max{function(column)} # SELECT max(function(column)) FROM table LIMIT 1
  # => 7

[Source]

     # File lib/sequel/dataset/actions.rb, line 404
404:     def max(column=Sequel.virtual_row(&Proc.new))
405:       aggregate_dataset.get{max(column).as(:max)}
406:     end

Returns the minimum value for the given column/expression. Uses a virtual row block if no argument is given.

  DB[:table].min(:id) # SELECT min(id) FROM table LIMIT 1
  # => 1
  DB[:table].min{function(column)} # SELECT min(function(column)) FROM table LIMIT 1
  # => 0

[Source]

     # File lib/sequel/dataset/actions.rb, line 415
415:     def min(column=Sequel.virtual_row(&Proc.new))
416:       aggregate_dataset.get{min(column).as(:min)}
417:     end

This is a front end for import that allows you to submit an array of hashes instead of arrays of columns and values:

  DB[:table].multi_insert([{:x => 1}, {:x => 2}])
  # INSERT INTO table (x) VALUES (1)
  # INSERT INTO table (x) VALUES (2)

Be aware that all hashes should have the same keys if you use this calling method, otherwise some columns could be missed or set to null instead of to default values.

This respects the same options as import.

[Source]

     # File lib/sequel/dataset/actions.rb, line 431
431:     def multi_insert(hashes, opts=OPTS)
432:       return if hashes.empty?
433:       columns = hashes.first.keys
434:       import(columns, hashes.map{|h| columns.map{|c| h[c]}}, opts)
435:     end

Yields each row in the dataset, but interally uses multiple queries as needed to process the entire result set without keeping all rows in the dataset in memory, even if the underlying driver buffers all query results in memory.

Because this uses multiple queries internally, in order to remain consistent, it also uses a transaction internally. Additionally, to work correctly, the dataset must have unambiguous order. Using an ambiguous order can result in an infinite loop, as well as subtler bugs such as yielding duplicate rows or rows being skipped.

Sequel checks that the datasets using this method have an order, but it cannot ensure that the order is unambiguous.

Options:

:rows_per_fetch :The number of rows to fetch per query. Defaults to 1000.
:strategy :The strategy to use for paging of results. By default this is :offset, for using an approach with a limit and offset for every page. This can be set to :filter, which uses a limit and a filter that excludes rows from previous pages. In order for this strategy to work, you must be selecting the columns you are ordering by, and none of the columns can contain NULLs. Note that some Sequel adapters have optimized implementations that will use cursors or streaming regardless of the :strategy option used.
:filter_values :If the :strategy=>:filter option is used, this option should be a proc that accepts the last retreived row for the previous page and an array of ORDER BY expressions, and returns an array of values relating to those expressions for the last retrieved row. You will need to use this option if your ORDER BY expressions are not simple columns, if they contain qualified identifiers that would be ambiguous unqualified, if they contain any identifiers that are aliased in SELECT, and potentially other cases.

Examples:

  DB[:table].order(:id).paged_each{|row| }
  # SELECT * FROM table ORDER BY id LIMIT 1000
  # SELECT * FROM table ORDER BY id LIMIT 1000 OFFSET 1000
  # ...

  DB[:table].order(:id).paged_each(:rows_per_fetch=>100){|row| }
  # SELECT * FROM table ORDER BY id LIMIT 100
  # SELECT * FROM table ORDER BY id LIMIT 100 OFFSET 100
  # ...

  DB[:table].order(:id).paged_each(:strategy=>:filter){|row| }
  # SELECT * FROM table ORDER BY id LIMIT 1000
  # SELECT * FROM table WHERE id > 1001 ORDER BY id LIMIT 1000
  # ...

  DB[:table].order(:table__id).paged_each(:strategy=>:filter,
    :filter_values=>proc{|row, exprs| [row[:id]]}){|row| }
  # SELECT * FROM table ORDER BY id LIMIT 1000
  # SELECT * FROM table WHERE id > 1001 ORDER BY id LIMIT 1000
  # ...

[Source]

     # File lib/sequel/dataset/actions.rb, line 488
488:     def paged_each(opts=OPTS)
489:       unless @opts[:order]
490:         raise Sequel::Error, "Dataset#paged_each requires the dataset be ordered"
491:       end
492:       unless block_given?
493:         return enum_for(:paged_each, opts)
494:       end
495: 
496:       total_limit = @opts[:limit]
497:       offset = @opts[:offset]
498:       if server = @opts[:server]
499:         opts = Hash[opts]
500:         opts[:server] = server
501:       end
502: 
503:       rows_per_fetch = opts[:rows_per_fetch] || 1000
504:       strategy = if offset || total_limit
505:         :offset
506:       else
507:         opts[:strategy] || :offset
508:       end
509: 
510:       db.transaction(opts) do
511:         case strategy
512:         when :filter
513:           filter_values = opts[:filter_values] || proc{|row, exprs| exprs.map{|e| row[hash_key_symbol(e)]}}
514:           base_ds = ds = limit(rows_per_fetch)
515:           while ds
516:             last_row = nil
517:             ds.each do |row|
518:               last_row = row
519:               yield row
520:             end
521:             ds = (base_ds.where(ignore_values_preceding(last_row, &filter_values)) if last_row)
522:           end
523:         else
524:           offset ||= 0
525:           num_rows_yielded = rows_per_fetch
526:           total_rows = 0
527: 
528:           while num_rows_yielded == rows_per_fetch && (total_limit.nil? || total_rows < total_limit)
529:             if total_limit && total_rows + rows_per_fetch > total_limit
530:               rows_per_fetch = total_limit - total_rows
531:             end
532: 
533:             num_rows_yielded = 0
534:             limit(rows_per_fetch, offset).each do |row|
535:               num_rows_yielded += 1
536:               total_rows += 1 if total_limit
537:               yield row
538:             end
539: 
540:             offset += rows_per_fetch
541:           end
542:         end
543:       end
544: 
545:       self
546:     end

Returns a Range instance made from the minimum and maximum values for the given column/expression. Uses a virtual row block if no argument is given.

  DB[:table].range(:id) # SELECT max(id) AS v1, min(id) AS v2 FROM table LIMIT 1
  # => 1..10
  DB[:table].interval{function(column)} # SELECT max(function(column)) AS v1, min(function(column)) AS v2 FROM table LIMIT 1
  # => 0..7

[Source]

     # File lib/sequel/dataset/actions.rb, line 555
555:     def range(column=Sequel.virtual_row(&Proc.new))
556:       if r = aggregate_dataset.select{[min(column).as(v1), max(column).as(v2)]}.first
557:         (r[:v1]..r[:v2])
558:       end
559:     end

Returns a hash with key_column values as keys and value_column values as values. Similar to to_hash, but only selects the columns given. Like to_hash, it accepts an optional :hash parameter, into which entries will be merged.

  DB[:table].select_hash(:id, :name) # SELECT id, name FROM table
  # => {1=>'a', 2=>'b', ...}

You can also provide an array of column names for either the key_column, the value column, or both:

  DB[:table].select_hash([:id, :foo], [:name, :bar]) # SELECT * FROM table
  # {[1, 3]=>['a', 'c'], [2, 4]=>['b', 'd'], ...}

When using this method, you must be sure that each expression has an alias that Sequel can determine. Usually you can do this by calling the as method on the expression and providing an alias.

[Source]

     # File lib/sequel/dataset/actions.rb, line 578
578:     def select_hash(key_column, value_column, opts = OPTS)
579:       _select_hash(:to_hash, key_column, value_column, opts)
580:     end

Returns a hash with key_column values as keys and an array of value_column values. Similar to to_hash_groups, but only selects the columns given. Like to_hash_groups, it accepts an optional :hash parameter, into which entries will be merged.

  DB[:table].select_hash_groups(:name, :id) # SELECT id, name FROM table
  # => {'a'=>[1, 4, ...], 'b'=>[2, ...], ...}

You can also provide an array of column names for either the key_column, the value column, or both:

  DB[:table].select_hash_groups([:first, :middle], [:last, :id]) # SELECT * FROM table
  # {['a', 'b']=>[['c', 1], ['d', 2], ...], ...}

When using this method, you must be sure that each expression has an alias that Sequel can determine. Usually you can do this by calling the as method on the expression and providing an alias.

[Source]

     # File lib/sequel/dataset/actions.rb, line 598
598:     def select_hash_groups(key_column, value_column, opts = OPTS)
599:       _select_hash(:to_hash_groups, key_column, value_column, opts)
600:     end

Selects the column given (either as an argument or as a block), and returns an array of all values of that column in the dataset. If you give a block argument that returns an array with multiple entries, the contents of the resulting array are undefined. Raises an Error if called with both an argument and a block.

  DB[:table].select_map(:id) # SELECT id FROM table
  # => [3, 5, 8, 1, ...]

  DB[:table].select_map{id * 2} # SELECT (id * 2) FROM table
  # => [6, 10, 16, 2, ...]

You can also provide an array of column names:

  DB[:table].select_map([:id, :name]) # SELECT id, name FROM table
  # => [[1, 'A'], [2, 'B'], [3, 'C'], ...]

If you provide an array of expressions, you must be sure that each entry in the array has an alias that Sequel can determine. Usually you can do this by calling the as method on the expression and providing an alias.

[Source]

     # File lib/sequel/dataset/actions.rb, line 622
622:     def select_map(column=nil, &block)
623:       _select_map(column, false, &block)
624:     end

The same as select_map, but in addition orders the array by the column.

  DB[:table].select_order_map(:id) # SELECT id FROM table ORDER BY id
  # => [1, 2, 3, 4, ...]

  DB[:table].select_order_map{id * 2} # SELECT (id * 2) FROM table ORDER BY (id * 2)
  # => [2, 4, 6, 8, ...]

You can also provide an array of column names:

  DB[:table].select_order_map([:id, :name]) # SELECT id, name FROM table ORDER BY id, name
  # => [[1, 'A'], [2, 'B'], [3, 'C'], ...]

If you provide an array of expressions, you must be sure that each entry in the array has an alias that Sequel can determine. Usually you can do this by calling the as method on the expression and providing an alias.

[Source]

     # File lib/sequel/dataset/actions.rb, line 642
642:     def select_order_map(column=nil, &block)
643:       _select_map(column, true, &block)
644:     end

Limits the dataset to one record, and returns the first record in the dataset, or nil if the dataset has no records. Users should probably use first instead of this method. Example:

  DB[:test].single_record # SELECT * FROM test LIMIT 1
  # => {:column_name=>'value'}

[Source]

     # File lib/sequel/dataset/actions.rb, line 652
652:     def single_record
653:       clone(:limit=>1).single_record!
654:     end

Returns the first record in dataset, without limiting the dataset. Returns nil if the dataset has no records. Users should probably use first instead of this method. This should only be used if you know the dataset is already limited to a single record. This method may be desirable to use for performance reasons, as it does not clone the receiver. Example:

  DB[:test].single_record! # SELECT * FROM test
  # => {:column_name=>'value'}

[Source]

     # File lib/sequel/dataset/actions.rb, line 664
664:     def single_record!
665:       with_sql_first(select_sql)
666:     end

Returns the first value of the first record in the dataset. Returns nil if dataset is empty. Users should generally use get instead of this method. Example:

  DB[:test].single_value # SELECT * FROM test LIMIT 1
  # => 'value'

[Source]

     # File lib/sequel/dataset/actions.rb, line 674
674:     def single_value
675:       if r = ungraphed.naked.single_record
676:         r.each{|_, v| return v}
677:       end
678:     end

Returns the first value of the first record in the dataset, without limiting the dataset. Returns nil if the dataset is empty. Users should generally use get instead of this method. Should not be used on graphed datasets or datasets that have row_procs that don‘t return hashes. This method may be desirable to use for performance reasons, as it does not clone the receiver.

  DB[:test].single_value! # SELECT * FROM test
  # => 'value'

[Source]

     # File lib/sequel/dataset/actions.rb, line 688
688:     def single_value!
689:       with_sql_single_value(select_sql)
690:     end

Returns the sum for the given column/expression. Uses a virtual row block if no column is given.

  DB[:table].sum(:id) # SELECT sum(id) FROM table LIMIT 1
  # => 55
  DB[:table].sum{function(column)} # SELECT sum(function(column)) FROM table LIMIT 1
  # => 10

[Source]

     # File lib/sequel/dataset/actions.rb, line 699
699:     def sum(column=Sequel.virtual_row(&Proc.new))
700:       aggregate_dataset.get{sum(column).as(:sum)}
701:     end

Returns a hash with one column used as key and another used as value. If rows have duplicate values for the key column, the latter row(s) will overwrite the value of the previous row(s). If the value_column is not given or nil, uses the entire hash as the value.

  DB[:table].to_hash(:id, :name) # SELECT * FROM table
  # {1=>'Jim', 2=>'Bob', ...}

  DB[:table].to_hash(:id) # SELECT * FROM table
  # {1=>{:id=>1, :name=>'Jim'}, 2=>{:id=>2, :name=>'Bob'}, ...}

You can also provide an array of column names for either the key_column, the value column, or both:

  DB[:table].to_hash([:id, :foo], [:name, :bar]) # SELECT * FROM table
  # {[1, 3]=>['Jim', 'bo'], [2, 4]=>['Bob', 'be'], ...}

  DB[:table].to_hash([:id, :name]) # SELECT * FROM table
  # {[1, 'Jim']=>{:id=>1, :name=>'Jim'}, [2, 'Bob'=>{:id=>2, :name=>'Bob'}, ...}

Options:

:all :Use all instead of each to retrieve the objects
:hash :The object into which the values will be placed. If this is not given, an empty hash is used. This can be used to use a hash with a default value or default proc.

[Source]

     # File lib/sequel/dataset/actions.rb, line 728
728:     def to_hash(key_column, value_column = nil, opts = OPTS)
729:       h = opts[:hash] || {}
730:       meth = opts[:all] ? :all : :each
731:       if value_column
732:         return naked.to_hash(key_column, value_column, opts) if row_proc
733:         if value_column.is_a?(Array)
734:           if key_column.is_a?(Array)
735:             send(meth){|r| h[r.values_at(*key_column)] = r.values_at(*value_column)}
736:           else
737:             send(meth){|r| h[r[key_column]] = r.values_at(*value_column)}
738:           end
739:         else
740:           if key_column.is_a?(Array)
741:             send(meth){|r| h[r.values_at(*key_column)] = r[value_column]}
742:           else
743:             send(meth){|r| h[r[key_column]] = r[value_column]}
744:           end
745:         end
746:       elsif key_column.is_a?(Array)
747:         send(meth){|r| h[key_column.map{|k| r[k]}] = r}
748:       else
749:         send(meth){|r| h[r[key_column]] = r}
750:       end
751:       h
752:     end

Returns a hash with one column used as key and the values being an array of column values. If the value_column is not given or nil, uses the entire hash as the value.

  DB[:table].to_hash_groups(:name, :id) # SELECT * FROM table
  # {'Jim'=>[1, 4, 16, ...], 'Bob'=>[2], ...}

  DB[:table].to_hash_groups(:name) # SELECT * FROM table
  # {'Jim'=>[{:id=>1, :name=>'Jim'}, {:id=>4, :name=>'Jim'}, ...], 'Bob'=>[{:id=>2, :name=>'Bob'}], ...}

You can also provide an array of column names for either the key_column, the value column, or both:

  DB[:table].to_hash_groups([:first, :middle], [:last, :id]) # SELECT * FROM table
  # {['Jim', 'Bob']=>[['Smith', 1], ['Jackson', 4], ...], ...}

  DB[:table].to_hash_groups([:first, :middle]) # SELECT * FROM table
  # {['Jim', 'Bob']=>[{:id=>1, :first=>'Jim', :middle=>'Bob', :last=>'Smith'}, ...], ...}

Options:

:all :Use all instead of each to retrieve the objects
:hash :The object into which the values will be placed. If this is not given, an empty hash is used. This can be used to use a hash with a default value or default proc.

to start with a new, empty hash.

[Source]

     # File lib/sequel/dataset/actions.rb, line 779
779:     def to_hash_groups(key_column, value_column = nil, opts = OPTS)
780:       h = opts[:hash] || {}
781:       meth = opts[:all] ? :all : :each
782:       if value_column
783:         return naked.to_hash_groups(key_column, value_column, opts) if row_proc
784:         if value_column.is_a?(Array)
785:           if key_column.is_a?(Array)
786:             send(meth){|r| (h[r.values_at(*key_column)] ||= []) << r.values_at(*value_column)}
787:           else
788:             send(meth){|r| (h[r[key_column]] ||= []) << r.values_at(*value_column)}
789:           end
790:         else
791:           if key_column.is_a?(Array)
792:             send(meth){|r| (h[r.values_at(*key_column)] ||= []) << r[value_column]}
793:           else
794:             send(meth){|r| (h[r[key_column]] ||= []) << r[value_column]}
795:           end
796:         end
797:       elsif key_column.is_a?(Array)
798:         send(meth){|r| (h[key_column.map{|k| r[k]}] ||= []) << r}
799:       else
800:         send(meth){|r| (h[r[key_column]] ||= []) << r}
801:       end
802:       h
803:     end

Truncates the dataset. Returns nil.

  DB[:table].truncate # TRUNCATE table
  # => nil

[Source]

     # File lib/sequel/dataset/actions.rb, line 809
809:     def truncate
810:       execute_ddl(truncate_sql)
811:     end

Updates values for the dataset. The returned value is generally the number of rows updated, but that is adapter dependent. values should a hash where the keys are columns to set and values are the values to which to set the columns.

  DB[:table].update(:x=>nil) # UPDATE table SET x = NULL
  # => 10

  DB[:table].update(:x=>Sequel[:x]+1, :y=>0) # UPDATE table SET x = (x + 1), y = 0
  # => 10

[Source]

     # File lib/sequel/dataset/actions.rb, line 823
823:     def update(values=OPTS, &block)
824:       sql = update_sql(values)
825:       if uses_returning?(:update)
826:         returning_fetch_rows(sql, &block)
827:       else
828:         execute_dui(sql)
829:       end
830:     end

Run the given SQL and return an array of all rows. If a block is given, each row is yielded to the block after all rows are loaded. See with_sql_each.

[Source]

     # File lib/sequel/dataset/actions.rb, line 834
834:     def with_sql_all(sql, &block)
835:       _all(block){|a| with_sql_each(sql){|r| a << r}}
836:     end

Execute the given SQL and return the number of rows deleted. This exists solely as an optimization, replacing with_sql(sql).delete. It‘s significantly faster as it does not require cloning the current dataset.

[Source]

     # File lib/sequel/dataset/actions.rb, line 841
841:     def with_sql_delete(sql)
842:       execute_dui(sql)
843:     end

Run the given SQL and yield each returned row to the block.

This method should not be called on a shared dataset if the columns selected in the given SQL do not match the columns in the receiver.

[Source]

     # File lib/sequel/dataset/actions.rb, line 850
850:     def with_sql_each(sql)
851:       if row_proc = @row_proc
852:         fetch_rows(sql){|r| yield row_proc.call(r)}
853:       else
854:         fetch_rows(sql){|r| yield r}
855:       end
856:       self
857:     end

Run the given SQL and return the first row, or nil if no rows were returned. See with_sql_each.

[Source]

     # File lib/sequel/dataset/actions.rb, line 861
861:     def with_sql_first(sql)
862:       with_sql_each(sql){|r| return r}
863:       nil
864:     end

Execute the given SQL and (on most databases) return the primary key of the inserted row.

[Source]

     # File lib/sequel/dataset/actions.rb, line 877
877:     def with_sql_insert(sql)
878:       execute_insert(sql)
879:     end

Run the given SQL and return the first value in the first row, or nil if no rows were returned. For this to make sense, the SQL given should select only a single value. See with_sql_each.

[Source]

     # File lib/sequel/dataset/actions.rb, line 869
869:     def with_sql_single_value(sql)
870:       if r = with_sql_first(sql)
871:         r.each{|_, v| return v}
872:       end
873:     end
with_sql_update(sql)

Alias for with_sql_delete

Protected Instance methods

Internals of import. If primary key values are requested, use separate insert commands for each row. Otherwise, call multi_insert_sql and execute each statement it gives separately.

[Source]

     # File lib/sequel/dataset/actions.rb, line 886
886:     def _import(columns, values, opts)
887:       trans_opts = Hash[opts].merge!(:server=>@opts[:server])
888:       if opts[:return] == :primary_key
889:         @db.transaction(trans_opts){values.map{|v| insert(columns, v)}}
890:       else
891:         stmts = multi_insert_sql(columns, values)
892:         @db.transaction(trans_opts){stmts.each{|st| execute_dui(st)}}
893:       end
894:     end

Return an array of arrays of values given by the symbols in ret_cols.

[Source]

     # File lib/sequel/dataset/actions.rb, line 897
897:     def _select_map_multiple(ret_cols)
898:       map{|r| r.values_at(*ret_cols)}
899:     end

Returns an array of the first value in each row.

[Source]

     # File lib/sequel/dataset/actions.rb, line 902
902:     def _select_map_single
903:       map{|r| r.values.first}
904:     end

6 - Miscellaneous methods

These methods don‘t fit cleanly into another section.

Constants

NOTIMPL_MSG = "This method must be overridden in Sequel adapters".freeze
ARRAY_ACCESS_ERROR_MSG = 'You cannot call Dataset#[] with an integer or with no arguments.'.freeze
ARG_BLOCK_ERROR_MSG = 'Must use either an argument or a block, not both'.freeze
IMPORT_ERROR_MSG = 'Using Sequel::Dataset#import an empty column array is not allowed'.freeze
DatasetClass = self
PREPARED_ARG_PLACEHOLDER = ':'.freeze
BindArgumentMethods = prepared_statements_module(:bind, ArgumentMapper)
PreparedStatementMethods = prepared_statements_module(:prepare, BindArgumentMethods)
DatasetClass = self
DatasetClass = self
DatasetClass = self
STREAMING_SUPPORTED = ::Mysql2::VERSION >= '0.3.12'
DatasetClass = self
PreparedStatementMethods = prepared_statements_module( "sql = self; opts = Hash[opts]; opts[:arguments] = bind_arguments", Sequel::Dataset::UnnumberedArgumentMapper, %w"execute execute_dui execute_insert")
OPTS = Sequel::OPTS

Attributes

columns  [W] 
db  [R]  The database related to this dataset. This is the Database instance that will execute all of this dataset‘s queries.
opts  [R]  The hash of options for this dataset, keys are symbols.

Public Class methods

Constructs a new Dataset instance with an associated database and options. Datasets are usually constructed by invoking the Database#[] method:

  DB[:posts]

Sequel::Dataset is an abstract class that is not useful by itself. Each database adapter provides a subclass of Sequel::Dataset, and has the Database#dataset method return an instance of that subclass.

[Source]

    # File lib/sequel/dataset/misc.rb, line 30
30:     def initialize(db)
31:       @db = db
32:       @opts = OPTS
33:     end

Public Instance methods

Define a hash value such that datasets with the same DB, opts, and SQL will be considered equal.

[Source]

    # File lib/sequel/dataset/misc.rb, line 37
37:     def ==(o)
38:       o.is_a?(self.class) && db == o.db && opts == o.opts && sql == o.sql
39:     end

Execute the given type of statement with the hash of values.

[Source]

     # File lib/sequel/adapters/sqlite.rb, line 314
314:       def call(type, bind_vars={}, *values, &block)
315:         ps = to_prepared_statement(type, values)
316:         ps.extend(BindArgumentMethods)
317:         ps.call(bind_vars, &block)
318:       end

An object representing the current date or time, should be an instance of Sequel.datetime_class.

[Source]

    # File lib/sequel/dataset/misc.rb, line 43
43:     def current_datetime
44:       Sequel.datetime_class.now
45:     end

Similar to clone, but returns an unfrozen clone if the receiver is frozen.

[Source]

    # File lib/sequel/dataset/misc.rb, line 53
53:     def dup
54:       o = clone
55:       o.instance_variable_set(:@frozen, false) if frozen?
56:       o
57:     end

Yield a dataset for each server in the connection pool that is tied to that server. Intended for use in sharded environments where all servers need to be modified with the same data:

  DB[:configs].where(:key=>'setting').each_server{|ds| ds.update(:value=>'new_value')}

[Source]

    # File lib/sequel/dataset/misc.rb, line 64
64:     def each_server
65:       db.servers.each{|s| yield server(s)}
66:     end

Alias for ==

[Source]

    # File lib/sequel/dataset/misc.rb, line 48
48:     def eql?(o)
49:       self == o
50:     end

Returns the string with the LIKE metacharacters (% and _) escaped. Useful for when the LIKE term is a user-provided string where metacharacters should not be recognized. Example:

  ds.escape_like("foo\\%_") # 'foo\\\%\_'

[Source]

    # File lib/sequel/dataset/misc.rb, line 73
73:     def escape_like(string)
74:       string.gsub(/[\\%_]/){|m| "\\#{m}"}
75:     end

Yield a hash for each row in the dataset.

[Source]

     # File lib/sequel/adapters/sqlite.rb, line 321
321:       def fetch_rows(sql)
322:         execute(sql) do |result|
323:           i = -1
324:           cps = db.conversion_procs
325:           type_procs = result.types.map{|t| cps[base_type_name(t)]}
326:           cols = result.columns.map{|c| i+=1; [output_identifier(c), i, type_procs[i]]}
327:           self.columns = cols.map(&:first)
328:           result.each do |values|
329:             row = {}
330:             cols.each do |name,id,type_proc|
331:               v = values[id]
332:               if type_proc && v
333:                 v = type_proc.call(v)
334:               end
335:               row[name] = v
336:             end
337:             yield row
338:           end
339:         end
340:       end

Yield all rows matching this dataset. If the dataset is set to split multiple statements, yield arrays of hashes one per statement instead of yielding results for all statements as hashes.

[Source]

     # File lib/sequel/adapters/sqlanywhere.rb, line 145
145:       def fetch_rows(sql)
146:         db = @db
147:         cps = db.conversion_procs
148:         api = db.api
149:         execute(sql) do |rs|
150:           convert = (convert_smallint_to_bool and db.convert_smallint_to_bool)
151:           col_infos = []
152:           api.sqlany_num_cols(rs).times do |i|
153:             _, _, name, _, type = api.sqlany_get_column_info(rs, i)
154:             cp = if type == 500
155:               cps[500] if convert
156:             else
157:               cps[type]
158:             end
159:             col_infos << [i, output_identifier(name), cp]
160:           end
161: 
162:           self.columns = col_infos.map{|a| a[1]}
163: 
164:           if rs
165:             while api.sqlany_fetch_next(rs) == 1
166:               h = {}
167:               col_infos.each do |i, name, cp|
168:                 _, v = api.sqlany_get_column(rs, i)
169:                 h[name] = cp && v ? cp[v] : v
170:               end
171:               yield h
172:             end
173:           end
174:         end
175:         self
176:       end

Yield all rows matching this dataset.

[Source]

     # File lib/sequel/adapters/mysql2.rb, line 255
255:       def fetch_rows(sql)
256:         execute(sql) do |r|
257:           self.columns = if identifier_output_method
258:             r.fields.map!{|c| output_identifier(c.to_s)}
259:           else
260:             r.fields
261:           end
262:           r.each(:cast_booleans=>convert_tinyint_to_bool?){|h| yield h}
263:         end
264:         self
265:       end

Set the columns and yield the hashes to the block.

[Source]

     # File lib/sequel/adapters/swift.rb, line 136
136:       def fetch_rows(sql)
137:         execute(sql) do |res|
138:           col_map = {}
139:           self.columns = res.fields.map do |c|
140:             col_map[c] = output_identifier(c)
141:           end
142:           tz = db.timezone if Sequel.application_timezone
143:           res.each do |r|
144:             h = {}
145:             r.each do |k, v|
146:               h[col_map[k]] = case v
147:               when StringIO
148:                 SQL::Blob.new(v.read)
149:               when DateTime
150:                 tz ? Sequel.database_to_application_timestamp(Sequel.send(:convert_input_datetime_no_offset, v, tz)) : v
151:               else
152:                 v
153:               end
154:             end
155:             yield h
156:           end
157:         end
158:         self
159:       end

Yield all rows matching this dataset. If the dataset is set to split multiple statements, yield arrays of hashes one per statement instead of yielding results for all statements as hashes.

[Source]

     # File lib/sequel/adapters/mysql.rb, line 299
299:       def fetch_rows(sql)
300:         execute(sql) do |r|
301:           i = -1
302:           cps = db.conversion_procs
303:           cols = r.fetch_fields.map do |f| 
304:             # Pretend tinyint is another integer type if its length is not 1, to
305:             # avoid casting to boolean if Sequel::MySQL.convert_tinyint_to_bool
306:             # is set.
307:             type_proc = f.type == 1 && cast_tinyint_integer?(f) ? cps[2] : cps[f.type]
308:             [output_identifier(f.name), type_proc, i+=1]
309:           end
310:           self.columns = cols.map(&:first)
311:           if opts[:split_multiple_result_sets]
312:             s = []
313:             yield_rows(r, cols){|h| s << h}
314:             yield s
315:           else
316:             yield_rows(r, cols){|h| yield h}
317:           end
318:         end
319:         self
320:       end

Alias of first_source_alias

[Source]

    # File lib/sequel/dataset/misc.rb, line 89
89:     def first_source
90:       first_source_alias
91:     end

The first source (primary table) for this dataset. If the dataset doesn‘t have a table, raises an Error. If the table is aliased, returns the aliased name.

  DB[:table].first_source_alias
  # => :table

  DB[:table___t].first_source_alias
  # => :t

[Source]

     # File lib/sequel/dataset/misc.rb, line 101
101:     def first_source_alias
102:       source = @opts[:from]
103:       if source.nil? || source.empty?
104:         raise Error, 'No source specified for query'
105:       end
106:       case s = source.first
107:       when SQL::AliasedExpression
108:         s.alias
109:       when Symbol
110:         _, _, aliaz = split_symbol(s)
111:         aliaz ? aliaz.to_sym : s
112:       else
113:         s
114:       end
115:     end

The first source (primary table) for this dataset. If the dataset doesn‘t have a table, raises an error. If the table is aliased, returns the original table, not the alias

  DB[:table].first_source_table
  # => :table

  DB[:table___t].first_source_table
  # => :table

[Source]

     # File lib/sequel/dataset/misc.rb, line 126
126:     def first_source_table
127:       source = @opts[:from]
128:       if source.nil? || source.empty?
129:         raise Error, 'No source specified for query'
130:       end
131:       case s = source.first
132:       when SQL::AliasedExpression
133:         s.expression
134:       when Symbol
135:         sch, table, aliaz = split_symbol(s)
136:         aliaz ? (sch ? SQL::QualifiedIdentifier.new(sch, table) : table.to_sym) : s
137:       else
138:         s
139:       end
140:     end

Sets the frozen flag on the dataset, so you can‘t modify it. Returns the receiver.

[Source]

    # File lib/sequel/dataset/misc.rb, line 78
78:     def freeze
79:       @frozen = true
80:       self
81:     end

Whether the object is frozen.

[Source]

    # File lib/sequel/dataset/misc.rb, line 84
84:     def frozen?
85:       @frozen == true
86:     end

Don‘t allow graphing a dataset that splits multiple statements

[Source]

     # File lib/sequel/adapters/mysql.rb, line 323
323:       def graph(*)
324:         raise(Error, "Can't graph a dataset that splits multiple result sets") if opts[:split_multiple_result_sets]
325:         super
326:       end

Define a hash value such that datasets with the same DB, opts, and SQL will have the same hash value

[Source]

     # File lib/sequel/dataset/misc.rb, line 144
144:     def hash
145:       [db, opts, sql].hash
146:     end

The String instance method to call on identifiers before sending them to the database.

[Source]

     # File lib/sequel/dataset/misc.rb, line 150
150:     def identifier_input_method
151:       if defined?(@identifier_input_method)
152:         @identifier_input_method
153:       else
154:         @identifier_input_method = db.identifier_input_method
155:       end
156:     end

The String instance method to call on identifiers before sending them to the database.

[Source]

     # File lib/sequel/dataset/misc.rb, line 160
160:     def identifier_output_method
161:       if defined?(@identifier_output_method)
162:         @identifier_output_method
163:       else
164:         @identifier_output_method = db.identifier_output_method
165:       end
166:     end

Returns a string representation of the dataset including the class name and the corresponding SQL select statement.

[Source]

     # File lib/sequel/dataset/misc.rb, line 170
170:     def inspect
171:       "#<#{visible_class_name}: #{sql.inspect}>"
172:     end

Whether this dataset is a joined dataset (multiple FROM tables or any JOINs).

[Source]

     # File lib/sequel/dataset/misc.rb, line 175
175:     def joined_dataset?
176:      !!((opts[:from].is_a?(Array) && opts[:from].size > 1) || opts[:join])
177:     end

Use streaming to implement paging if Mysql2 supports it.

[Source]

     # File lib/sequel/adapters/mysql2.rb, line 268
268:       def paged_each(opts=OPTS, &block)
269:         if STREAMING_SUPPORTED
270:           stream.each(&block)
271:         else
272:           super
273:         end
274:       end

Create a named prepared statement that is stored in the database (and connection) for reuse.

[Source]

     # File lib/sequel/adapters/mysql2.rb, line 243
243:         def prepare(type, name=nil, *values)
244:           ps = to_prepared_statement(type, values)
245:           ps.extend(PreparedStatementMethods)
246:           if name
247:             ps.prepared_statement_name = name
248:             db.set_prepared_statement(name, ps)
249:           end
250:           ps
251:         end

Prepare the given type of query with the given name and store it in the database. Note that a new native prepared statement is created on each call to this prepared statement.

[Source]

     # File lib/sequel/adapters/sqlite.rb, line 345
345:       def prepare(type, name=nil, *values)
346:         ps = to_prepared_statement(type, values)
347:         ps.extend(PreparedStatementMethods)
348:         if name
349:           ps.prepared_statement_name = name
350:           db.set_prepared_statement(name, ps)
351:         end
352:         ps
353:       end

The alias to use for the row_number column, used when emulating OFFSET support and for eager limit strategies

[Source]

     # File lib/sequel/dataset/misc.rb, line 181
181:     def row_number_column
182:       :x_sequel_row_number_x
183:     end

Splits a possible implicit alias in c, handling both SQL::AliasedExpressions and Symbols. Returns an array of two elements, with the first being the main expression, and the second being the alias.

[Source]

     # File lib/sequel/dataset/misc.rb, line 188
188:     def split_alias(c)
189:       case c
190:       when Symbol
191:         c_table, column, aliaz = split_symbol(c)
192:         [c_table ? SQL::QualifiedIdentifier.new(c_table, column.to_sym) : column.to_sym, aliaz]
193:       when SQL::AliasedExpression
194:         [c.expression, c.alias]
195:       when SQL::JoinClause
196:         [c.table, c.table_alias]
197:       else
198:         [c, nil]
199:       end
200:     end

Makes each yield arrays of rows, with each array containing the rows for a given result set. Does not work with graphing. So you can submit SQL with multiple statements and easily determine which statement returned which results.

Modifies the row_proc of the returned dataset so that it still works as expected (running on the hashes instead of on the arrays of hashes). If you modify the row_proc afterward, note that it will receive an array of hashes instead of a hash.

[Source]

     # File lib/sequel/adapters/mysql.rb, line 337
337:       def split_multiple_result_sets
338:         raise(Error, "Can't split multiple statements on a graphed dataset") if opts[:graph]
339:         ds = clone(:split_multiple_result_sets=>true)
340:         ds.row_proc = proc{|x| x.map{|h| row_proc.call(h)}} if row_proc
341:         ds
342:       end

Return a clone of the dataset that will stream rows when iterating over the result set, so it can handle large datasets that won‘t fit in memory (Requires mysql 0.3.12+ to have an effect).

[Source]

     # File lib/sequel/adapters/mysql2.rb, line 279
279:       def stream
280:         clone(:stream=>true)
281:       end

This returns an SQL::Identifier or SQL::AliasedExpression containing an SQL identifier that represents the unqualified column for the given value. The given value should be a Symbol, SQL::Identifier, SQL::QualifiedIdentifier, or SQL::AliasedExpression containing one of those. In other cases, this returns nil

[Source]

     # File lib/sequel/dataset/misc.rb, line 207
207:     def unqualified_column_for(v)
208:       unless v.is_a?(String)
209:         _unqualified_column_for(v)
210:       end
211:     end

Creates a unique table alias that hasn‘t already been used in the dataset. table_alias can be any type of object accepted by alias_symbol. The symbol returned will be the implicit alias in the argument, possibly appended with "_N" if the implicit alias has already been used, where N is an integer starting at 0 and increasing until an unused one is found.

You can provide a second addition array argument containing symbols that should not be considered valid table aliases. The current aliases for the FROM and JOIN tables are automatically included in this array.

  DB[:table].unused_table_alias(:t)
  # => :t

  DB[:table].unused_table_alias(:table)
  # => :table_0

  DB[:table, :table_0].unused_table_alias(:table)
  # => :table_1

  DB[:table, :table_0].unused_table_alias(:table, [:table_1, :table_2])
  # => :table_3

[Source]

     # File lib/sequel/dataset/misc.rb, line 235
235:     def unused_table_alias(table_alias, used_aliases = [])
236:       table_alias = alias_symbol(table_alias)
237:       used_aliases += opts[:from].map{|t| alias_symbol(t)} if opts[:from]
238:       used_aliases += opts[:join].map{|j| j.table_alias ? alias_alias_symbol(j.table_alias) : alias_symbol(j.table)} if opts[:join]
239:       if used_aliases.include?(table_alias)
240:         i = 0
241:         loop do
242:           ta = "#{table_alias}_#{i}""#{table_alias}_#{i}"
243:           return ta unless used_aliases.include?(ta)
244:           i += 1 
245:         end
246:       else
247:         table_alias
248:       end
249:     end