题解 | 先试错,后改错
使用join查询方式找出没有分类的电影id以及名称
https://www.nowcoder.com/practice/a158fa6e79274ac497832697b4b83658
select f.film_id,f.title from film f left join film_category fc on f.film_id=fc.film_id left join category c on fc.category_id=c.category_id where c.category_id is null