Re: Big tables

Raimundo,

why do you multiply the number of rows of your tables? Sure you will have some selection criteria on your tables so no (!) dbms actually does build the cartesian product when you join tables instead it uses any available information about your tables to construct an optimal access path to your data and a very efficient access path to data are indexes im many cases.

Regards,

Harry

In article <38AAB479.2ACBE99E_at_medicina.ub.es>,   Raimundo Lozano <rlozano_at_medicina.ub.es> wrote:
> Hi Heinz,
>
> Heinz Huber wrote:
>
> > I think the most important issue in dealing with largly populated
 tables
> > and also with a big number of joins are indexes. Given good
 selectivity,
> > the right indexes should speed queries (and joins) up big time.
> >
>
> I agree with you about the utility of indexes. But if you have a join
 between
> 5 tables, every one with a million of rows, the DBMS have to deal
 with a
> number of rows of 100000000... until 30 "0s". I think is a number
 greater than
> the number of atoms in the Universe. I know that the optimizer of the
 DBMS can
> reduce that number, but do you think that only with right indexes is
 enough?
>
> Raimundo Lozano
>
>

Sent via Deja.com http://www.deja.com/
Before you buy. Received on Thu Feb 17 2000 - 00:00:00 CET