Re: Index Behaviour

On July 6, 2001 04:51 pm, Mercadante, Thomas F wrote:
> Dave,
>
> I think <> is like using the NOT operator, thus an index can not be
> used.
>
> Think about it - your asking the optimizer to find records in the
> index that are not there - nothing to really search on - so it does
> a FTS.
>
> Now if you did
>
> select surnam from basic where membno between 0 and 9
> or membno between 10 and 10000
>
> it might work as expected.

You also have to realize it may be quicker to do a full table scan. Consider a table with 1000 records, 100 of which are membno 10 - 90% of the table is not #10 - it would be much quicker to do a scan of the table instead of looking up all the records in the index then grabbing the corresponding rows from the table.

Cheers,
GC

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