题解 | #使用子查询的方式找出属于Action分类的所有电影对应的title,description#

答案

select title, description
from film
where film_id in (
    select fc.film_id
    from category c, film_category fc
    where c.category_id = fc.category_id
    and c.name = 'Action'/*查询action分类的电影id*/
    );

思路

1. 查询action分类的电影id

   select fc.film_id
   from category c, film_category fc
   where c.category_id = fc.category_id
   and c.name = 'Action'

2. 查询电影id在1中的电影title，description

优化

可以完全不用join，使用3个子查询解答

select title, description
from film
where film_id in (
    select film_id
    from film_category /*查询action分类的film_id*/
    where category_id in (
        select category_id
        from category
        where name = 'Action'/*查询action分类的category_id*/
        )
    );