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Multiple Column Joins

  • November 6, 2013 at 12:44 pm

    #300021

    I have two tables and I need to join on one column if there is a match else join on another

    Example

    SELECT

    tb1.Col1

    , tb2.Col2

    , tb2.Col3

    FROM TB1

    LEFT OUTER JOIN TB2

    ON tb1.Col1 = tb2.Col1

    OR tb1.Col2 = tb2.Col2

    Problem is, using OR the performance is horrible, what is a more efficient way of doing this?

  • November 6, 2013 at 12:48 pm

    #1664547

    you could use a union to do the same thing:

    select tb1.Col1, tb2.Col2, tb2.Col3

    from TB1

    left outer join TB2 on tb2.Col1 = tb2.Col1

    union

    select tb1.Col1, tb2.Col2, tb2.Col3

    from TB1

    left outer join TB2 on tb2.Col2 = tb2.Col2


    Microsoft Certified Master - SQL Server 2008
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  • November 6, 2013 at 1:26 pm

    #1664556

    That is perfect!! Before, the query that I was running took over 6 minutes to run. This one ran seconds. Thank you very much!!!

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