diff options
Diffstat (limited to 'activerecord/lib/active_record/relation/calculations.rb')
| -rw-r--r-- | activerecord/lib/active_record/relation/calculations.rb | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb index 42c9881b48..56cf9bcd27 100644 --- a/activerecord/lib/active_record/relation/calculations.rb +++ b/activerecord/lib/active_record/relation/calculations.rb @@ -19,6 +19,14 @@ module ActiveRecord # # Person.group(:city).count # # => { 'Rome' => 5, 'Paris' => 3 } + # + # If +count+ is used with +select+, it will count the selected columns: + # + # Person.select(:age).count + # # => counts the number of different age values + # + # Note: not all valid +select+ expressions are valid +count+ expressions. The specifics differ + # between databases. In invalid cases, an error from the databsae is thrown. def count(column_name = nil, options = {}) # TODO: Remove options argument as soon we remove support to # activerecord-deprecated_finders. |