Re: Question on NULLs in index

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
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 - 08:18:51 CDT