28.【较难】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，而且还需要该分类包含电影总数量>=5部

一开始我是这样写

select c.name as '分类名称category.name',
       count(f.film_id) as '电影数目count(film.film_id)'
from film f,category c,film_category fc
where f.film_id=fc.film_id
and fc.category_id=c.category_id
and f.description like '%robot%'
group by c.name
having count(fc.category_id)>=5

很显然对蓝色标记部分理解不对

应该先找到每个电影分类下电影总数量大于5的category_id，修改如下

正确代码

select c.name,
       count(fc.film_id)
from film f,category c,film_category fc
where f.description like '%robot%'
and f.film_id=fc.film_id
and fc.category_id=c.category_id
and c.category_id in (select category_id
                      from film_category
                      group by category_id
                       having count(film_id)>=5)