Performance Tips Part 2

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  • Re: Situation 6

    I don't get the use of variables and table type variables for what is essentially a set-based validation:


      SELECT external_item_cd

      FROM inserted

      WHERE external_item_cd IS NOT NULL

      GROUP BY external_item_cd

      HAVING COUNT(*) > 1



        RAISERROR('Duplicate Records', 16, 1)




    Same with the 2nd step, why count to compare counts, when all you need to test for is existence

    IF EXISTS  (

        SELECT 1

        FROM Item As t1

        INNER JOIN inserted As i

          ON ( i.external_item_cd = t1.external_item_cd )

        WHERE EXISTS (

          SELECT 1

          FROM Item As t2

          WHERE t2.external_item_cd = t1.external_item_cd

          AND   t2.ItemID <> t1.ItemID




  • To start with, the idea seems to be to prevent duplications. But the trigger's code suggests that only duplications are to be allowed. Something wrong in the code.

    Kindest Regards,

    M Suresh Kumar

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