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Aggregate Performance Question

  • May 30, 2018 at 9:41 am

    #368609

    Which approach should I generally take? In this example, I'm keeping it simple, but imagine 20 calculated columns in which I keep summing the same values repeatedly, just in different combinations.  Or what if I have 10 when lines in my case, where I keep using the same sum values?

    Method One

    select a, b = sum(b), c = case when sum(z) < sum(b) then 'Yes' from Table group by a

    Method Two

    select a, b, c = case when z < b then 'Yes'
    from (
    select a, b = sum(b), z = sum(z) from Table group by a
    ) x

  • May 30, 2018 at 11:19 am

    #1992356

    Use method two.  You could also use a view or a cte to define the SUMs to use in other calcs.

    SQL DBA,SQL Server MVP(07, 08, 09) A socialist is someone who will give you the shirt off *someone else's* back.

  • May 30, 2018 at 11:32 am

    #1992358

    Thanks.

  • May 30, 2018 at 11:50 am

    #1992364

    There shouldn't be any performance difference, but the second method might reduce the length of the code by not having to repeat it.

    Luis C.
    General Disclaimer:
    Are you seriously taking the advice and code from someone from the internet without testing it? Do you at least understand it? Or can it easily kill your server?

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