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Can I say that 'Clustered index scan' equals to 'table scan'? Or what is the difference?

  • June 23, 2010 at 2:56 pm

    #387210

    I am learning some basics about TSQL performance tuning. Some of the terms are confusing to me. Could somebody answer this simple question? Thanks.

  • June 23, 2010 at 3:55 pm

    #1184236

    A table scan is a read of all the data pages of a table that does not have a clustered index

    A clustered index scan is a read of all the data pages of a table that does have a clustered index

    http://sqlinthewild.co.za/index.php/2007/11/15/execution-plan-operations-scans-and-seeks/

    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

  • June 23, 2010 at 7:30 pm

    #1184272

    hl6a (6/23/2010)

    I am learning some basics about TSQL performance tuning. Some of the terms are confusing to me. Could somebody answer this simple question? Thanks.

    The simple answer is "Yes" with the semantical differences that Gail noted above. Performance wise, one is just as bad (or good, depending) as the other.

    {edit} And, I definitely recommend the link that Gail pointed you to.

    --Jeff Moden

    RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
    First step towards the paradigm shift of writing Set Based code:
    ________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

    Change is inevitable... Change for the better is not.

    Helpful Links:
    How to post code problems
    How to Post Performance Problems
    Create a Tally Function (fnTally)

  • June 24, 2010 at 6:46 am

    #1184465

    Thanks so much for the answers and more!

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