Re: index on null column

From: Darrell Landrum <DLANDRUM_at_zalecorp.com>
Date: Fri, 28 Mar 2003 12:08:52 -0800
Message-ID: <F001.00575815.20030328120852@fatcity.com>

AK,
I'd still do some testing with a bitmap index on that column. You have 1,000,000 records. 500 records have value in that column. That means the absolute most distinct values in that column is 501. This is at least one criteria for bitmap candidacy. What I see in testing is select * from table where A = 'some value' can use the bitmap index. Also I see select * from table where A is null also uses the bitmap index.
I'm definitely not saying this as 'end all', just saying it might be worth playing with.

Darrell Landrum
Database Administrator
Zale Corporation

>>> oramagic_at_hotmail.com 03/28/03 09:59AM >>>
It means if I do a query with where clause with A=:x its going to go for
index .
Does oracle go to table if :x is null. It looks like it does . ???

-ak

• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Thursday, March 27, 2003 6:33 PM

> AK
> Yes, it will benefit the non-null records. Just remember that the
null
> values aren't indexes.
>
>
>
> Dennis Williams
> DBA, 40%OCP, 100% DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
> -----Original Message-----
> Sent: Thursday, March 27, 2003 5:19 PM
> To: Multiple recipients of list ORACLE-L
>
>
> I have a table with column A. there are 1000000 records in table out
of
> which 500o records has not null in column A rest are null.
> if i created an index on A, will it benefit .
>
> thanks,
> ak
>
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.net
> --
> Author: DENNIS WILLIAMS
> INET: DWILLIAMS_at_LIFETOUCH.COM
>
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-- 
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-- 
Author: AK
  INET: oramagic_at_hotmail.com 

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Author: Darrell Landrum
  INET: DLANDRUM_at_zalecorp.com

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Received on Fri Mar 28 2003 - 14:08:52 CST