Improving performance on joins to large tables.

  • Comments posted to this topic are about the item Improving performance on joins to large tables.

  • Here u can improve performance more by specifying column names rather than using "*". Because using * queries sys.columns system table for get the column names, which is unnecessary when we can simply specify them.

    But you have to remember to update SP when u change the table(columns).


  • SQL has to do meta-data lookups whether or not * is specified as it has to find the types and the column lengths.

    The reasons to not use select * are more around only retrieving the columns that you need and not returning all of them out of laziness. It's also so that code won't break if a new clumn is added to a table. finally, select * makes creating covering indexes almost impossible.

    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

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