Distinct-On.md

@@ -5,6 +5,7 @@ MySQL-like group by statement on queries. It keeps only the first row of each se
 distinct_on(*columns)
 ```
 
+Just send the list of fields to be included on the `DISTINCT ON` statement:
 ```ruby
 # SELECT DISTINCT ON ( "users"."name" ) "users".* FROM "users"
 User.distinct_on(:name).all
@@ -12,6 +13,9 @@ User.distinct_on(:name).all
 
 You can use where-like syntax to find more complex columns:
 ```ruby
-# SELECT DISTINCT ON ( "users"."name" ) "users".* FROM "users"
-User.distinct_on(:name).all
+# SELECT DISTINCT ON ( "photos"."type" ) "users".* FROM "users" INNER JOIN "photos" ON "users"."id" = "photos"."user_id"
+User.joins(:photos).distinct_on(photos: :type).all
+
+# SELECT DISTINCT ON ( "photos"."type", "photos"."size" ) "users".* FROM "users" INNER JOIN "photos" ON "users"."id" = "photos"."user_id"
+User.joins(:photos).distinct_on(photos: [:type, :size]).all
 ```
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