练习一下EXISTS的用法
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
https://www.nowcoder.com/practice/2f2e556d335d469f96b91b212c4c203e
SELECT title,description
FROM film f
WHERE EXISTS(
SELECT * FROM film_category
LEFT JOIN category USING(category_id)
WHERE name='Action' AND film_id=f.film_id
)