Re: Creating Indexes

From: Alan Shein <alanshein_at_erols.com>
Date: Thu, 18 Nov 1999 10:16:29 -0500
Message-ID: <81157e$5ll$1@autumn.news.rcn.net>

If you are always querying the three fields in the same order, and always using field 1, such as:

1
1,2
1,2,3

then you can create a composite index that will work just as efficiently as three individual indexes. If you'll need to query in some other way, such as

2

2,1
2,3
3,2,1
3,1

etc...

then you may want to use individual indexes.

Greg Stark <greg-spare-1_at_mit.edu> wrote in message news:87pux8mnys.fsf_at_HSE-Montreal-ppp19485.qc.sympatico.ca...
>
> "Steve McDaniels" <steve.mcdaniels_at_sierra.com> writes:
>
> > The fastest possible INDEX strategy (in this context) is to index each
field
> > separately.
>
> why is this useful? I have queries that use two or three fields each of
which
> are indexed separately but Oracle just does a range scan using one of them
> ignoring the rest. I would love to be able to combine multiple indexes but
I
> can't see how Oracle could do that with B-tree indexes. Can it?
>
>
> --
> greg
Received on Thu Nov 18 1999 - 09:16:29 CST