UPDATE Sql cannot have aggregate in set

Question

What's the work around to this error:

An aggregate may not appear in the set list of an UPDATE statement.

I've looked at a few examples but not really sure.

This is what I have now:

 UPDATE UserAnswer 
 SET userId = (SELECT id FROM Users WHERE id=max(id)) 
 WHERE userId = NULL

Answer 1

This may solve the issue, you need to make the max in the select list.

UPDATE UserAnswer 
SET userId = (SELECT Max(id) FROM Users) 
WHERE userId is NULL

Answer 2

You can try MAX OR Order By :

MAX:

UPDATE UserAnswer 
SET userId = (SELECT MAX(id) FROM Users) 
WHERE userId = NULL

Order By:

UPDATE UserAnswer 
SET userId = (SELECT TOP(1) id FROM Users Order By id DESC) 
WHERE userId = NULL

Answer 3

Try using a variable, like this:

DECLARE @maxId INT;

SELECT @maxId = MAX(id)
FROM Users;

UPDATE UserAnswer
SET userId = @maxId
WHERE userId IS NULL;