# Write your MySQL query statement below
select ACTOR_ID,DIRECTOR_ID from ActorDirector group by actor_id,director_id having count(director_id)>=3
可以看出sql允许通过多个字段进行group by。
筛选null值可以通过 is not NULL解决
# Write your MySQL query statement below
select ACTOR_ID,DIRECTOR_ID from ActorDirector group by actor_id,director_id having count(director_id)>=3
可以看出sql允许通过多个字段进行group by。
筛选null值可以通过 is not NULL解决