Question

I wan’t to update a column if a certain userid was found in a log for violations.

UPDATE 
USER_CHECK_LOGIN
SET 
CHECKLOGIN = 2
WHERE 
USER_CHECK_LOGIN.USER_ID = (SELECT NAME from XTREME.gamelogs.dbo.LOG_USING_DEPOT201211 WHERE GATENUM=150);

What this query does is, if a userid is found in the logs where the gatenum is 150, all users will be banned.

But I seem to get an error.

Msg 512, Level 16, State 1, Line 2
Subquery returned more than 1 value. This is not permitted when the subquery follows =,     !=, <, <= , >, >= or when the subquery is used as an expression.
The statement has been terminated.

Answer 1

Instead of =, use IN() since the subquery is expected to return multiple rows. Using = in comparison against a subquery return value assumes only one row with one column is returned.

USER_CHECK_LOGIN.USER_ID IN (SELECT NAME from XTREME.gamelogs.dbo.LOG_USING_DEPOT201211 WHERE GATENUM=150);