Re: density calculation when histograms are involved
- From: "LS Cheng" <exriscer@xxxxxxxxx>
- To: rjoralist@xxxxxxxxxxxxxxxxxxxxx
- Date: Thu, 13 Sep 2007 23:03:59 +0200
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@xxxxxxxxxxxxxxxxxxxxx> 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.
> >
> >
>
>
> --
> //www.freelists.org/webpage/oracle-l
>
>
>
Other related posts:
