Class: Sequel::SQL::VirtualRow
- Inherits:
- BasicObject
- Includes:
- OperatorBuilders
- Defined in:
- lib/sequel/sql.rb,
lib/sequel/extensions/virtual_row_method_block.rb
Overview
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.
Instance Method Summary collapse
-
#initialize ⇒ VirtualRow
constructor
A new instance of VirtualRow.
Methods included from OperatorBuilders
Methods inherited from BasicObject
Constructor Details
#initialize ⇒ VirtualRow
Returns a new instance of VirtualRow.
1910 1911 1912 |
# File 'lib/sequel/sql.rb', line 1910 def initialize freeze end |