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Re: NULL Values in Indexes - Confused

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Thu, 12 Aug 1999 15:43:26 +0100
Message-ID: <934469540.4295.1.nnrp-04.9e984b29@news.demon.co.uk>

Unless the index was a bitmap index -
which might be totally unsuitable for your application anyway, and with a 10% hit rate Oracle might calculate the FTS to be the optimum strategy anyway.

--

Jonathan Lewis
Yet another Oracle-related web site: http://www.jlcomp.demon.co.uk

Thomas Kyte wrote in message <37b2ced2.68295153_at_newshost.us.oracle.com>...
>A copy of this was sent to Dipen Kotecha <dkotecha_at_ford.invalid>
>(if that email address didn't require changing)
>On Thu, 12 Aug 1999 15:01:20 +0200, you wrote:
>
>>We have a table with 1.2 million records which is regularly queried to
>>see whether a date field is NULL. I understand that NULL values are not
>>stored in indexes, so if I created an index on this date field, would it
>>be used in the query? Approx. 10% of the data contains a NULL date
>>field.
>>
>>Dipen
>
>A query such as:
>
>select * from T where X is null;
>
>will never use an index. The rows where X is null would not be stored in
an
>index on X.
>
>A full scan would result.
>
Received on Thu Aug 12 1999 - 09:43:26 CDT

Original text of this message

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