ORDER BY with DELETE not working - mysql

Question

I have written this delete query to remove the duplicate entries from table but when I run this query it will keep the old rows and delete the newest one. I want to keep the newest inserted rows and want to delete the old ones. I have appended ORDER BY clause in delete query but it's not working.
DELETE t2
FROM user_deprovision t1
JOIN user_deprovision t2 ON (
t2.UserName = t1.UserName AND
t2.GroupName = t1.Groupname AND
t2.id > t1.id)
ORDER BY t1.DeletedDate;
How can I achieve this.

Answer 1

Let's write a query that returns the latest time for a user name and group name.
SELECT
UserName, GroupName, MAX(deprovision_time)
FROM
user_deprovision
GROUP BY
UserName, GroupName
Now, let's adapt this to your purpose. In Oracle, I might do something to turn that into a temporary table, but I'll use correlated subqueries here instead.
DELETE FROM user_deprovision AS dp1
WHERE dp1.deprovision_time <
ANY (SELECT deprovision_time FROM user_deprovision AS dp2
WHERE dp1.UserName = dp2.UserName
AND dp1.GroupName = dp2.GroupName);
We can turn this into a join instead.
SELECT dp1.id
FROM user_deprovision AS dp1
JOIN user_deprovision AS dp2
ON dp1.UserName = dp2.UserName
AND dp1.GroupName = dp2.GroupName
WHERE
dp1.deprovision_time < dp2.deprovision_time
And the corresponding delete is:
DELETE FROM user_deprovision
WHERE id IN (
SELECT dp1.id
FROM user_deprovision AS dp1
JOIN user_deprovision AS dp2
ON dp1.UserName = dp2.UserName
AND dp1.GroupName = dp2.GroupName
WHERE
dp1.deprovision_time < dp2.deprovision_time);