hmm, and how do you do with foreign key that have only very few
value? cause foreign key automatiquelly create index !

thanks
stephane

--- In firebird-support@yahoogroups.com, "Adam" <s3057043@...> wrote:
>
> --- In firebird-support@yahoogroups.com, "Sasa Mihajlovic"
> <majstoru@> wrote:
> >
> > Hi,
> >
> > few days ago I was do the Database Statistics and in the report I
have
> > some bad indexes, for example I have a field session which is
represent
> > a fiscal year in table invoices. so do I need to index that field
> > because I have only 3-5 different values and I often use this
field in
> > my sql statetmets like very important in where clausule?
> >
>
> Usually such poor selectivity will make performance worse. Indices
can
> only be of benefit if they eliminate the need to read data pages
from
> disk. When there are so many duplicates, the chances of being able
to
> ignore an entire data page is reduced to near 0.
>
> Adam
>