mysql语句查重复记录⼤于1的_在MySQL中删除计数⼤于1
的重复⾏
Need some help on a MySQL query to delete the rows where the userID count is greater than one and has an acl value=4. What I've tried as the select query:
DELETE FROM `users_acl`
WHERE userID IN(
SELECT * FROM `users_acl`
WHERE `acl` BETWEEN 2 AND 4
GROUP BY userID
HAVING COUNT(userID) > 1
);
But can't find a proper way to delete the rows in the same query.
Table structure
+--------+-----+---------+
| userID | acl | deleted |
+--------+-----+---------+
| 27 | 2 | 0 |
| 28 | 2 | 0 |
| 31 | 2 | 0 |
| 42 | 2 | 0 |
| 42 | 4 | 0 |
| 45 | 1 | 0 |
| 51 | 1 | 0 |mysql删除重复的数据保留一条
| 54 | 1 | 0 |
| 63 | 2 | 0 |
| 63 | 4 | 0 |
| 64 | 1 | 0 |
| 69 | 2 | 0 |
| 73 | 2 | 0 |
| 73 | 4 | 0 |
| 76 | 1 | 0 |
| 77 | 2 | 0 |
| 77 | 4 | 0 |
+--------+-----+---------+
解决⽅案
In MySQL you can't select from a table you are deleting from at the same time. But with a temp table you can overcome this problem
DELETE FROM `users_acl`
WHERE userID IN
(
SELECT * FROM
(
SELECT userID
FROM `users_acl`
GROUP BY userID
HAVING COUNT(userID) > 1
AND SUM(`acl` = 4) > 0
) tmp
);
or use a joininstead
DELETE u
FROM `users_acl` u
JOIN
(
SELECT userID
FROM `users_acl`
GROUP BY userID
HAVING COUNT(userID) > 1
AND SUM(`acl` = 4) > 0
) tmp on tmp.userID = u.userID

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