Msg 164, Level 15, State 1, Line 2
Each GROUP BY expression must contain at least one column that is not an outer reference.
This error message appears when you try to use only expressions in a GROUP BY clause that are interpreted as outer references.
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. Every GROUP BY clause must contain at least one column that is not interpreted as outer reference.
All versions of SQL Server.
IF OBJECT_ID(‘tempdb..#t’) > 0
DROP TABLE #t
CREATE TABLE #t
INSERT INTO #t SELECT 1, ‘1’;
GROUP BY 2
In the above example the GROUP BY 5 clause is interpreted as outer reference, because it cannot be associated with the inner statement. This raises the error.