Re: density calculation when histograms are involved

Hi

I've got the book but I am a bit confused in the part where it talks about selectivity and histograms in page 43 which says

10g uses num_distinct to work out the selectivity which is cardinality = num_rows / num_distinct if there is histogram then cardinality = num_rows * density

but I am in 9i so.... I am also reading chapter 7 btw

Thanks

--
LSC


On 9/13/07, Rich Jesse <rjoralist_at_society.servebeer.com> wrote:


>

> Might as well complete the list with Jonathan's Cost-Based Oracle

> Fundamentals:

>

> http://www.apress.com/book/view/1590596366

>

> At a $25 steal for the eBook, it's been open on my desktop for two solid

> months now (I'm only on chapter 7!).

>

> Rich

>

> > Hi Cheng,

> >

> >

> >

> > Recommend you to read:

> >

> >

> >

> > 1st: Wolfgang's

> > http://www.centrexcc.com/Histograms%20-%20Myths%20and%20Facts.pdf

> >

> >

> >

> > 2nd: Alberto Dell'Era "Join over Histograms" paper :

> > http://www.adellera.it/investigations/join_over_histograms/JoinOverHisto

> > grams.pdf  (covering much more complex cases)

> >

> >

> >

> > regards.

> >

> >

>

>

> --

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

>

>

>


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