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Diffstat (limited to 'guides')
| -rw-r--r-- | guides/source/active_record_querying.textile | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/guides/source/active_record_querying.textile b/guides/source/active_record_querying.textile index a9cb424eaa..294ef25b33 100644 --- a/guides/source/active_record_querying.textile +++ b/guides/source/active_record_querying.textile @@ -1260,6 +1260,24 @@ with Client.pluck(:id) </ruby> +h3. +ids+ + ++ids+ can be used to pluck all the IDs for the relation using the table's primary key. + +<ruby> +Person.ids +# SELECT id FROM people +</ruby> + +<ruby> +class Person < ActiveRecord::Base + self.primary_key = "person_id" +end + +Person.ids +# SELECT person_id FROM people +</ruby> + h3. Existence of Objects If you simply want to check for the existence of the object there's a method called +exists?+. This method will query the database using the same query as +find+, but instead of returning an object or collection of objects it will return either +true+ or +false+. |