I would like so as to add details about pair (fa1.actor_id, fa2.actor_id), however I do not understand how.

And I all the time get error like should seem within the GROUP BY clause or be utilized in an combination operate

I would like one thing like

choose actors_comparing.first_actor, actors_comparing.second_actor, max(actors_comparing.counta)
from (
  SELECT fa1.actor_id first_actor, fa2.actor_id second_actor, depend counta
  FROM film_actor fa1
  be a part of film_actor fa2
  utilizing (film_id)
  the place fa1.actor_id != fa2.actor_id
  group by (fa1.actor_id, fa2.actor_id)
) actors_comparing