题解 | #使用join查询方式找出没有分类的电影id以及名称#
select film_id,title from film where film_id not in (select f.film_id from film as f join category as c join film_category as fc on fc.film_id = f.film_id and fc.category_id = c.category_id )
step 1: 先根据film_category联合出完整的电影表 step 2: film 做一下集合查询 in