题解 | #SQL29 用 join 方式找出没有分类的电影 id 及其名称#

select t.film_id, t.title from 
(select f.film_id, fy.category_id, f.title from film f left join film_category fy on f.film_id = fy.film_id) as t  
left join category c on c.category_id = t.category_id
where t.category_id is null