.distinct or .uniq

If you want to remove duplicates from a result, you can use .distinct():

Customers.select(:country).distinct

This queries the database as follows:

SELECT DISTINCT "customers"."country" FROM "customers"

.uniq() has the same effect. With Rails 5.0 it got deprecated and it will be removed from Rails with version 5.1. The reason is, that the word unique doesn’t have the same meaning as distinct and it can be misleading. Furthermore distinct is closer to the SQL syntax.