SQL: Delete by result of Select with Join

Question

I have the following mySQL Query which returns a list of ID's. I want to delete the rows with each ID of the list from the table "serverking_user"

SELECT serverking_user.id FROM (serverking_user
INNER JOIN serverking_logins
ON serverking_user.id=serverking_logins.uid)
WHERE serverking_logins.time < 3600
GROUP BY serverking_user.id
HAVING COUNT(serverking_logins.login) = 1

One possibility would be to loop through each ID by using "in". But since "in" is deactivated on my Sql Server I need to solve this with a "join".

Any ideas ?

Answer 1

It has been a while since I have done MySQL development, but if I remember correctly this should work for you:

DELETE su
FROM serverking_user su
INNER JOIN serverking_logins sl
ON su.id=sl.uid
WHERE sl.time < 3600
GROUP BY su.id
HAVING COUNT(sl.login) = 1

In general, if you want to delete records from a single table in a JOIN, you just specify that table (or its alias) after DELETE

UPDATED QUERY
It seems that MySQL isn't fond of deleting where a grouped query is involved, so another possibility is to use an anti-join. However, I'm sure that the performance characteristics of this query will be suboptimal. It may be better to use two separate queries instead. Nonetheless, here is a solution using anti-joins:

DELETE su
FROM serverking_user su
INNER JOIN serverking_logins sl
ON su.id=sl.uid
LEFT JOIN serverking_logins antisl
ON sl.uid = antisl.uid
AND sl.id <> antisl.id
WHERE sl.time < 3600
AND antisl.id IS NULL

Answer 2

Perhaps you could store the results of the select inside of a table variable and then join that?

declare @Ids table
(
  Id int
);

insert into @Ids (Id)
SELECT serverking_user.id FROM (serverking_user
INNER JOIN serverking_logins
ON serverking_user.id=serverking_logins.uid)
WHERE serverking_logins.time < 3600
GROUP BY serverking_user.id
HAVING COUNT(serverking_logins.login) = 1;

delete yt from YourTable yt
inner join @Ids Ids on Ids.Id = yt.id;

Note that the consistency of this depends on your transaction configuration, since you're doing two separate queries here.

Answer 3

DELETE FROM serverking_user
WHERE EXISTS
(SELECT *
FROM (serverking_user
INNER JOIN serverking_logins
ON serverking_user.id=serverking_logins.uid)
WHERE serverking_logins.time < 3600
GROUP BY serverking_user.id
HAVING COUNT(serverking_logins.login) = 1) a