mysql - 删除在单独表中找不到 userID 的行

Question

如果我运行以下 SQL 语句:

SELECT * FROM `user-data` t1 
LEFT JOIN `users` t2 ON t1.userID = t2.id 
WHERE t2.id IS NULL

它为我提供了 users 表中没有匹配行的所有行(因为用户已被删除)。但我不能简单地将其转换为 DELETE 语句:

DELETE FROM `user-data` t1 
LEFT JOIN `users` t2 ON t1.userID = t2.id 
WHERE t2.id IS NULL

当我收到以下错误时:

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 't1 
LEFT JOIN `users` t2 ON t1.userID = t2.id 
WHERE t2.id IS NULL' at line 1

如何删除 user-data 中表 users 中没有现有用户的所有行？

Answer 1

不要使用 LEFT OUTER JOIN 和 IS NULL 尝试 WHERE NOT EXISTS。像这样:

DELETE t1
FROM user-data t1
WHERE NOT EXISTS
(
SELECT id FROM FROM users WHERE user-data.userID = users.id)
)