Re: how do columns affect one another (theory question)?

On Mon, 3 Jun 2002 20:39:32 -0700, "Marc E" <marc_e_at_cablespeed.com> wrote:

>Hi all,
> I have a database theory question. Let's say I have two columns:
>MyInteger and MyBlob.
>
>The table contains 100,000 rows. If I run a select statement against just
>the MyInteger column, with no reference to any other table, do the contents
>of the MyBlob column affect the performance of my query?
>
>Put another way, if I have 2 MB of MyInteger Data, and 1000 GB of MyBlob
>data, and I just want to get at some of the MyInteger data, does that 1000
>GB of MyBlob data have any impact on my query?
>
>Thanks for input.
>
>Marc
>

If you select one column of a record, the whole record is fetched in buffer cache. In your case it depends whether the BLOBs are stored inline or in a separate blob segment.
However, I have been working with an application where there was a long in a table. The long was needed in only one program, but logically belonged to that table. The long was also on average 40k, the rest a few measly bytes. Now you guess what happened. We created a separate table with the primary key of the original table and the long.

Hth

Sybrand Bakker, Senior Oracle DBA

To reply remove -verwijderdit from my e-mail address Received on Tue Jun 04 2002 - 00:00:29 CDT