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density values too high

  • February 24, 2010 at 6:36 am

    #216007

    Hi,

    DBCC SHOW_STATISTICS (TBL_PHOTO,PK_TBL_PHOTO)

    updated date - Feb 2 2010 8:01PM

    density values - 3.5829964E-6

    This density values too high, I think this index may not be use.

    How can recreate the exitsting PK? If i recreate pk what about data existing data? can you suggestion me,

    thanks

  • February 24, 2010 at 11:31 am

    #1124428

    Too high? That's a value of 0.0000035. Why do you think that's too high and why do you think that the index isn't useful?

    Density is defined as 1/(number of unique values in the table)

    Since a primary key is always unique (no duplicate) it has the lowest possible density for the table (single column pk)

    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

  • February 24, 2010 at 9:42 pm

    #1124741

    Thank you Gila for your reply, I got it clear myside about how density as defined.

    In SQL SERVER By default auto update enabled in this database, why agian create another Update statistics?

    Could you tell me, Update statistics jobs, Is it really space consuming activity?

    Thanks.

  • February 25, 2010 at 12:20 am

    #1124771

    ananda.murugesan (2/24/2010)

    In SQL SERVER By default auto update enabled in this database, why agian create another Update statistics?

    Because sometimes autoupdate doesn't update often enough

    Could you tell me, Update statistics jobs, Is it really space consuming activity?

    No.

    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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