null value eliminated by an aggregate operation

  • i am getting the following warning on running my query:-

    Warning: The join order has been enforced because a local join hint is used.

    Warning: Null value is eliminated by an aggregate or other SET operation.

    the query has a union from subqueries .tables in some subqueries do not have corresponding cols in other subquery,hence they are written as null..the subquery has group by condition but for all the columns in group by condition,i have handled them with isnull(x,y) function.

    cannot ignore this warning,since when i run the query through a stored proc in ssis package,it fails

  • "Warning: Null value is eliminated by an aggregate or other SET operation"

    This is probably caused by having ANSI_WARNINGS on and an aggregate on a column which contains a null value.

    e.g.

    SET ANSI_WARNINGS ON

    DECLARE @TABLE AS TABLE(Col1 INT, Col2 INT)

    INSERT INTO @TABLE(Col1, Col2)

    SELECT 1, 1 UNION ALL

    SELECT 1, 2 UNION ALL

    SELECT 1, 3 UNION ALL

    SELECT 2, 1 UNION ALL

    SELECT 2, Null UNION ALL

    SELECT 2, 3

    SELECT Col1, SUM(Col2), COUNT(Col2), AVG(Col2)

    FROM @TABLE

    GROUP BY Col1

    So, you can eliminate it by setting ANSI_WARNINGS off or eliminating the NULL values from the query.

    "Warning: The join order has been enforced because a local join hint is used"

    This is because you've added a HINT to a join. The chances are pretty good that doing this was wrong, almost all of the time the optimiser knows what it's doing and should be left alone. If you're in one of the very very rare cases where this is not applicable, you could add OPTION (FORCE ORDER) to your query to stop SQL Server warning you that it is going to enforce the ordering.


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