1、category表与film_category表 内连接,查询属于Action分类的所有电影id
select b.film_id from category a join film_category b on a.category_id=b.category_id where a.name='Action'2、在film中查询1表中电影id对应的电影信息
select title,description from film where film_id in (select b.film_id from category a join film_category b on a.category_id=b.category_id where a.name='Action');