Msg 158, Level 15, State 1, Line 2
An aggregate may not appear in the OUTPUT clause.
This error message appears when you try to use an aggregate function in the OUTPUT clause of an UPDATE statement.
The T-SQL statement can be parsed, but causes the error at runtime.
Error of the Severity level 15 are generated by the user and can be fixed by the SQL Server user. Aggregate functions are not allowed in the OUTPUT clause.
This error message was introduced with SQL Server 2005.
IF OBJECT_ID(‘tempdb..#t’) > 0
DROP TABLE #t
CREATE TABLE #t
INSERT INTO #t SELECT 1;
UPDATE #t SET c1 = 2
In the above example we try to use the SUM() aggregate function in the OUTPUT clause of an UPDATE statement. This raises the error.