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IF EXIST - DO NOTHING

  • October 6, 2011 at 4:39 pm

    #1391528

    If you're going to rollback, you need a begin transaction, however you don't need a rollback, at the point you have it there's nothing to rollback

    You also don't need that second check.

    IF EXISTS (...)

    RAISERROR (...);

    RETURN;

    ELSE

    INSERT ...

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

  • October 9, 2011 at 3:45 pm

    #1392226

    I do believe much from the business logics shown above that the query below with AND gates is the correct one

    if not exists (select 1 from customer where col_1 = X and col_2 = Y and col_3 = Z)

    begin

    end

    [font="Arial Black"]Performance Guard[/font]

    [font="Courier New"]Just ask me to get 0 sec for all queries[/font]

  • October 10, 2011 at 12:50 am

    #1392272

    i agree. i did the test below:

    it is your logic underneath the condition that changes based on exist and not exist, not your "and" and "or" gates:

    declare @temp table

    (

    a varchar(50),

    b varchar(50),

    c varchar(50)

    )

    insert into @temp values('a','b','c')

    if not exists (select 1 from @temp where a = 'a' AND b = 'b' AND c = 'c')

    print 'do something'

    else print 'do nothing'

    if exists (select 1 from @temp where a = 'a' AND b = 'b' AND c = 'c')

    print 'do nothing'

    else print 'do something'

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