How to fix error in SQL query

Question

How to fix error in SQL query.

Answer 1

Where did I make a mistake?

Nearly everywhere. If you want to use aggregation function, the in common we use a GROUP BY clause. Try it with

SELECT A.actor_id, A.first_name, A.last_name, COUNT(*) AS CountFims
FROM actor AS A
     LEFT JOIN
     film_actor AS F
        ON A.actor_id = F.actor_id
GROUP BY A.actor_id, A.first_name, A.last_name
HAVING COUNT(*) < 20 

Answer 2

;with cte as (select actor_id, count(film_id) as cntFilms from film_actor group by actor_Id having count(film_id) < 20)
select a.* from Actor  a join cte on a.actor_Id = cte.Actor_ID