题解 | #查找描述信息中包含robot的电影对应的分类名称以及电影数目，而且还需要该分类对应电影数量>=5部#

1. 把电影数>=5的类别从film_category里挑出来，形成new_fc；
2. 把三张表连起来，且加入限制description里有robot，形成new_f;
3. 按照category_id把new_fc和new_f连起来，按照category去group之后计数count(*)即可。

代码：
select new_f.name, count(*) from

(select c.category_id, c.name
from film f, category c, film_category fc
where f.film_id = fc.film_id and c.category_id = fc.category_id
and f.description like '%robot%') as new_f

join

(select fc.category_id from film_category fc
group by fc.category_id
having count(*) >=5) as new_fc

on new_f.category_id = new_fc.category_id
group by new_f.category_id