FAQ
List,

Can anyone tell me the index selectivity formula for a column when
there are histograms on the column.
I know that the index selectivity without histograms is =
num_distinct/num_rows and also know that table selectivity uses
density to calculate the selectivty when there are histograms placed
on the column.

Thanks,
--
Best Regards,
Syed Jaffar Hussain
8i,9i & 10g, OCP DBA
Banque Saudi Fransi,
Saudi Arabia
http://jaffardba.blogspot.com/

"Winners don't do different things. They do things differently."
--
http://www.freelists.org/webpage/oracle-l

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  • Jared Still at Mar 27, 2006 at 7:50 pm
    The explanation is found in Jonathan Lewis' CBO book:

    http://www.amazon.com/gp/product/1590596366

    There is a rather extensive chapter on histgrams, and it
    does cover selectivity.

    Jared
    On 3/21/06, The Human Fly wrote:

    List,

    Can anyone tell me the index selectivity formula for a column when
    there are histograms on the column.
    I know that the index selectivity without histograms is =
    num_distinct/num_rows and also know that table selectivity uses
    density to calculate the selectivty when there are histograms placed
    on the column.

    Thanks,
    --
    Best Regards,
    Syed Jaffar Hussain
    8i,9i & 10g, OCP DBA
    Banque Saudi Fransi,
    Saudi Arabia
    http://jaffardba.blogspot.com/

    ----------------------------------------------------------------------------------
    "Winners don't do different things. They do things differently."
    --
    http://www.freelists.org/webpage/oracle-l

    --
    Jared Still
    Certifiable Oracle DBA and Part Time Perl Evangelist

    --
    http://www.freelists.org/webpage/oracle-l

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postedMar 21, '06 at 3:57p
activeMar 27, '06 at 7:50p
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