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#

子查询，下面的SQL逻辑很清晰。

#最后用film_id查电影表中的title与description
select title,description from film where film_id IN (
    #再用查到的categoryid查询对应关系表中的film_id 
    select film_id from film_category where category_id IN (
        #先在分类表中查分类名为Action的category_id 
        select category_id from category where name = "Action"
    )
)

连接查询

select f.title,f.description
from film as f
#电影表与关系表合并
left join film_category as fc
    on f.film_id = fc.film_id
#关系表与分类表合并
left join category as c
    on fc.category_id = c.category_id
where c.name = "Action";