Question: Who are the top 5 actors with the highest number of films? List their full names and calculate the average number of films for each of the actors.
SQL: SELECT T.first_name, T.last_name, num FROM ( SELECT T1.first_name, T1.last_name, COUNT(T2.film_id) AS num FROM actor AS T1 INNER JOIN film_actor AS T2 ON T1.actor_id = T2.actor_id INNER JOIN film AS T3 ON T2.film_id = T3.film_id GROUP BY T1.first_name, T1.last_name ) AS T ORDER BY T.num DESC LIMIT 5