需要MySQL查询的帮助

Question

请帮我解决这个MySQL查询。我已经玩了很长时间了。也许它需要一双新鲜的眼睛。

两个表格：锁定和会话

locks
--------------
id session_id
--------------
1  sajf4$Jf9422jd
2  2jf*4j2okg9092
3  J8j4j4ffss93o2
------------------

sessions
-------------------------
id              user_id
-------------------------
sajf4$Jf9422jd  14
J8j4j4ffss93o2  14
2jf*4j2okg9092  21
-------------------------

我想删除其中user_id为session = 14

的锁中的所有行

Answer 1

DELETE FROM locks 
WHERE session_id IN (SELECT id FROM sessions WHERE user_id = 14)

Answer 2

DELETE FROM locks WHERE session_id =（SELECT id FROM sessions WHERE user_id = 14）;

Answer 3

从其中session_id的锁中删除（select_id来自其中user_id = 14的会话）

Answer 4

没有子查询的另一种方法：

从锁中删除  使用锁  在sessions.id = locks.session_id上加入会话  其中sessions.user_id = 14

Answer 5

DELETE locks, sessions FROM locks INNER JOIN sessions WHERE locks.session_id=sessions.id;