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| author | Yves Senn <yves.senn@gmail.com> | 2014-05-13 09:04:46 +0200 |
|---|---|---|
| committer | Yves Senn <yves.senn@gmail.com> | 2014-05-13 09:04:52 +0200 |
| commit | ef8ac1f88522d098534361a10c2da50bc81753fd (patch) | |
| tree | 8a677561e496e5d9a3084f27121532a2e92ad7b8 | |
| parent | 55b1f21ae361b585e3ff0e991703a47ab4887dd0 (diff) | |
| download | rails-ef8ac1f88522d098534361a10c2da50bc81753fd.tar.gz rails-ef8ac1f88522d098534361a10c2da50bc81753fd.tar.bz2 rails-ef8ac1f88522d098534361a10c2da50bc81753fd.zip | |
docs, explain usage of `count` + `select`. Closes #15065. [ci skip]
| -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. |