找出合作过三次的演员和导演

• GROUP BY actor_id, director_id：按照 actor_id 和 director_id 的组合进行分组，这样可以将每个演员和导演的合作记录归为一组。
• HAVING COUNT(*) >= 3：对每个分组进行统计，筛选出记录数量大于等于 3 的分组，也就是合作次数大于等于 3 次的演员和导演组合

• # 新建表
  create table actordirector
  (actor_id int not null,
  director_id int not null,
  timestamp int not null,
  primary key(timestamp));
  #查询
  select * from actordirector;
  #插入数据
  insert into actordirector values
  (1,1,0),
  (1,1,1),
  (1,1,2),
  (1,2,3),
  (1,2,4),
  (2,1,5),
  (2,1,6);
  insert into actordirector values (1,1,2);
  
  # 找出至少合作过三次的演员和导演

• 

   自己写的嵌套是错误的

• select director_id,actor_id
  from actordirector
  where actor_id in (
  select actor_id
  from actordirector
  group by actor_id
  having count(actor_id)>=3
  )
  group by director_id
  having count(director_id)>=3;