SELECT f.title,f.description FROM film f LEFT JOIN film_category fi ON f.film_id=fi.film_id LEFT JOIN category c ON fi.category_id=c.category_id WHERE c.name='Action'
两次左外连接,一次筛选
SELECT f.title,f.description FROM film f LEFT JOIN film_category fi ON f.film_id=fi.film_id LEFT JOIN category c ON fi.category_id=c.category_id WHERE c.name='Action'
两次左外连接,一次筛选