diff options
| -rw-r--r-- | activerecord/lib/active_record/relation/calculations.rb | 33 |
1 files changed, 27 insertions, 6 deletions
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb index 0044c49c1d..aa2f325f74 100644 --- a/activerecord/lib/active_record/relation/calculations.rb +++ b/activerecord/lib/active_record/relation/calculations.rb @@ -108,15 +108,36 @@ module ActiveRecord 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 |