Distinct On

This is an old version of this page. You can view the most recent version or browse the history.

MySQL-like group by statement on queries. It keeps only the first row of each set of rows where the given expressions evaluate to equal. PostgreSQL Docs

How it works

distinct_on(*columns)

# SELECT DISTINCT ON ( "users"."name" ) "users".* FROM "users"
User.distinct_on(:name).all

You can use where-like syntax to find more complex columns:

# SELECT DISTINCT ON ( "users"."name" ) "users".* FROM "users"
User.distinct_on(:name).all