irb(main):014:0> Post.where(:tag => "test").pluck(:title).uniq (3.4ms) SELECT title FROM "posts" WHERE "posts"."tag" = 'test' => ["title1", "title2"] irb(main):015:0> Post.where(:tag => "test").uniq.pluck(:title) (5.3ms) SELECT DISTINCT title FROM "posts" WHERE "posts"."tag" = 'test' => ["title1", "title2"]