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#

首先三张表内连接，条件为film表的描述信息包含robot也就是 like '%robot%'，还有一个隐含条件(所有分类的电影数量>=5)
SELECT
    t3.name,
    count(t1.film_id)
FROM
    film AS t1
inner JOIN
    film_category AS t2
on 
    t1.film_id=t2.film_id
INNER join 
    category AS t3
ON 
    t2.category_id=t3.category_id
where
    t1.description LIKE '%robot%'
and
    t2.category_id 
IN 
    (select category_id from film_category group by category_id having count(film_id)>=5)