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体验新版 GitCode,发现更多精彩内容 >>
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ea50d53d
编写于
5月 15, 2012
作者:
J
Jeremy Kemper
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差异文件
Expand and improve #pluck docs
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3f352d04
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+27
-6
activerecord/lib/active_record/relation/calculations.rb
activerecord/lib/active_record/relation/calculations.rb
+27
-6
未找到文件。
activerecord/lib/active_record/relation/calculations.rb
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ea50d53d
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@@ -108,15 +108,36 @@ def calculate(operation, column_name, options = {})
0
end
# This method is designed to perform select by a single column as direct SQL query
# Returns <tt>Array</tt> with values of the specified column name
# The values has same data type as column.
# Use <tt>pluck</tt> as a shortcut to select a single attribute without
# loading a bunch of records just to grab one attribute you want.
#
# Person.pluck(:name)
#
# instead of
#
# Person.all.map(&:name)
#
# Pluck returns an <tt>Array</tt> of attribute values type-casted to match
# the plucked column name, if it can be deduced. Plucking a SQL fragment
# returns String values by default.
#
# Examples:
#
# Person.pluck(:id) # SELECT people.id FROM people
# Person.uniq.pluck(:role) # SELECT DISTINCT role FROM people
# Person.where(:age => 21).limit(5).pluck(:id) # SELECT people.id FROM people WHERE people.age = 21 LIMIT 5
# Person.pluck(:id)
# # SELECT people.id FROM people
# # => [1, 2, 3]
#
# Person.uniq.pluck(:role)
# # SELECT DISTINCT role FROM people
# # => ['admin', 'member', 'guest']
#
# Person.where(:age => 21).limit(5).pluck(:id)
# # SELECT people.id FROM people WHERE people.age = 21 LIMIT 5
# # => [2, 3]
#
# Person.pluck('DATEDIFF(updated_at, created_at)')
# # SELECT DATEDIFF(updated_at, created_at) FROM people
# # => ['0', '27761', '173']
#
def
pluck
(
column_name
)
key
=
column_name
.
to_s
.
split
(
'.'
,
2
).
last
...
...
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