Class Sequel::SQL::VirtualRow
In: lib/sequel/extensions/virtual_row_method_block.rb
lib/sequel/sql.rb
Parent: BasicObject

The purpose of the VirtualRow class is to allow the easy creation of SQL identifiers and functions, in a way that leads to more compact code.

An instance of this class is yielded to the block supplied to Dataset#where, Dataset#order, and Dataset#select (and the other methods that accept a block and pass it to one of those methods). If the block doesn‘t take an argument, the block is instance_execed in the context of an instance of this class.

VirtualRow uses method_missing to return either an Identifier, Function depending on how it is called.

Function :Returned if any arguments are supplied, using the method name as the function name, and the arguments as the function arguments.
Identifier :Returned otherwise, using the method name.

If splitting symbols has been enabled (not the default), then method calls without arguments will return QualifiedIdentifier instances if the method call includes a double underscore.

Examples:

  ds = DB[:t]

  # Argument yielded to block
  ds.where{|r| r.name < 2} # SELECT * FROM t WHERE (name < 2)

  # Block without argument (instance_exec)
  ds.where{name < 2} # SELECT * FROM t WHERE (name < 2)

  # Functions
  ds.where{is_active(1, 'arg2')} # SELECT * FROM t WHERE is_active(1, 'arg2')
  ds.select{version.function} # SELECT version() FROM t
  ds.select{count.function.*} # SELECT count(*) FROM t
  ds.select{count(col1).distinct} # SELECT count(DISTINCT col1) FROM t

  # Math Operators
  ds.select{|o| o.+(1, :a).as(:b)} # SELECT (1 + a) AS b FROM t
  ds.select{|o| o.-(2, :a).as(:b)} # SELECT (2 - a) AS b FROM t
  ds.select{|o| o.*(3, :a).as(:b)} # SELECT (3 * a) AS b FROM t
  ds.select{|o| o./(4, :a).as(:b)} # SELECT (4 / a) AS b FROM t

  # Boolean Operators
  ds.where{|o| o.&({a: 1}, :b)}    # SELECT * FROM t WHERE ((a = 1) AND b)
  ds.where{|o| o.|({a: 1}, :b)}    # SELECT * FROM t WHERE ((a = 1) OR b)
  ds.where{|o| o.~(a: 1)}        # SELECT * FROM t WHERE (a != 1)
  ds.where{|o| o.~(a: 1, b: 2)} # SELECT * FROM t WHERE ((a != 1) OR (b != 2))

  # Inequality Operators
  ds.where{|o| o.>(1, :a)}  # SELECT * FROM t WHERE (1 > a)
  ds.where{|o| o.<(2, :a)}  # SELECT * FROM t WHERE (2 < a)
  ds.where{|o| o.>=(3, :a)} # SELECT * FROM t WHERE (3 >= a)
  ds.where{|o| o.<=(4, :a)} # SELECT * FROM t WHERE (4 <= a)

For a more detailed explanation, see the Virtual Rows guide.

Methods

new  

Included Modules

Module OperatorBuilders Module

Public Class methods

[Source]

      # File lib/sequel/sql.rb, line 1848
1848:       def initialize
1849:         freeze
1850:       end

[Validate]