Postgreas unique and order by conflict, what's wrong?

Question

PostgreSQL

The expression of the form
.joins(:user => :profile).order_site_rating
gives duplicates, how and why I have not figured it out yet, if you tell me, I will also be glad.
The problem is the following
PG conflicts if we just add distinct

joins(:user => :profile).order_site_rating.distinct

Asks to add an expression from there to select and everything would be fine if

SELECT DISTINCT(users.id), users.*, profiles.first_name FROM users LEFT JOIN profiles ON users.id = profiles.user_id ORDER BY profiles.first_name

But unfortunately the selection is very difficult.

order('case when profiles.avatar is null then -1 else 1 end desc')

How can I add this to the select or how to fix the links so that there are no duplicates in the selection?

Answer 1

ERROR: in a SELECT DISTINCT construct, the ORDER BY expressions must be in the select list
LINE 1: ...("anketa_owners"."town_id" IS NOT NULL) ORDER BY case when ...
^
: SELECT DISTINCT "anketa_owners".* FROM " anketa_owners" INNER JOIN "users" ON "users"."id" = "anketa_owners"."user_id" INNER JOIN "profiles" ON "profiles"."user_id" = "users"."id" WHERE ("anketa_owners". "town_id" IS NOT NULL) ORDER BY case when profiles.avatar is null then -1 else 1 end desc, profiles.rating DESC LIMIT 10 OFFSET 0