Re: Which index to create ?

From: Keith Jamieson <keith_jamieson_at_hotmail.com>
Date: Mon, 8 Dec 2003 11:01:53 -0000
Message-ID: <JSYAb.3668$nm6.19128@news.indigo.ie>

What makes you think that the full tablescan is the performance bottleneck? As far as I can see you are selecting all the rows in the table therefore a full table scan is quite appropriate.

Keith Jamieson

"André Hartmann" <andrehartmann_at_hotmail.com> wrote in message news:3fd43484$1_at_olaf.komtel.net...
> Hi,
>
> I have a question regarding the tuning of one of my SQL statements.
> Suppose there is a table X in my Schema which has columns A, B, C (all
> INTEGER) where A is the primary key. Suppose further that the table is
> pretty large: 10 million rows or more. Quite frequently I want to do this
> statement:
>
> SELECT DISTINCT B FROM X
>
> The explain plan tells me there is a full table scan on X. So I thought it
> might help to create an index on the B column but I still get a full table
> scan. I believe that the full table scan is the main performance
> bottleneck... how can I get rid of the full table scan ?
>
> André
>
>
Received on Mon Dec 08 2003 - 05:01:53 CST