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Update stats question

  • June 16, 2011 at 2:36 pm

    #242333

    Hi everyone,

    What is the difference between Update stats with full scan and Update stats with 50% sampling?

    Thank you.

  • June 16, 2011 at 2:48 pm

    #1340081

    The fullscan reads the entire table. The sampling 50% reads around 50% of the table (a sample)

    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 16, 2011 at 3:57 pm

    #1340113

    So, whenver I've to do Update stats, can I just do 50% sampling instead of fullscan?

  • June 16, 2011 at 4:20 pm

    #1340118

    Um...

    Sure, if you don't mind that SQL is only reading half the table (a random half) to compute the statistics. Half the table != the entire table.

    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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