Re: Question on NULLs in index

Bert Scalzo wrote:
>
> The rules are:
>
> 1. NULLS are not stored in B-TREE indexes, and thus where clauses with IS
> NULL or IS NOT NULL will do full tables scans

I believe IS NOT NULL will use the index.

Paul

>
> 2. BITMAP indexes do handle NULL values, but since BITMAPs work with the
> cost based optimizer -- the statistics and/or histograms you gather may
> still make the full table scan appear more desireable
>
> The point is that NULLs and indexes generally don't go together in Oracle
> explain plans.
>
> Bert Scalzo
> DBA
> EDS
Received on Wed Jul 15 1998 - 15:32:07 CDT