最近在接受采访时,我遇到了以下问题:
我有一个包含以下表的数据库(为了这个例子,让我们说这些表是有意义的):
我想找到购买电影“黑暗骑士”的顾客的名字。
我的回答是:
SELECT name FROM User AS u
INNER JOIN CreditCard AS cc ON u.id = cc.id
INNER JOIN Purchase AS p ON p.movie_id =
(SELECT id FROM Movie AS m WHERE m.name = "Dark Knight") AND cc.id = p.cc_id
除了语法之外,我想知道这是否是解决此问题的更有效方法。
答案 0 :(得分:3)
最好只加入movie
表,不要加入creditcard
SELECT u.name
FROM `User` AS u
INNER JOIN Purchase AS p ON p.cc_id = u.cc_id
INNER JOIN movie m on p.movie_id = m.id
WHERE m.name = 'Dark Knight'
答案 1 :(得分:1)
SELECT name from User as u
JOIN CreditCards as cc on cc.id = u.cc_id
JOIN Purchase AS p ON p.cc_id = c.id
JOIN Movie AS m on m.id = p.movie_id
WHERE m.name = 'Dark Night';