"Merlin Moncure" <merlin.moncure@rcsonline.com> writes:
> > select * from sometable where somefield IS NULL won't work because IS
> is
> > not a nomally indexible operator.
>
> Ah, I didn't know that. So there is no real reason not to exclude null
> values from all your indexes :). Reading Tom's recent comments
> everything is clear now.
There are other reasons. If you want a query like
SELECT * FROM tab ORDER BY col LIMIT 10
to use an index on col then it can't exclude NULLs or else it wouldn't be
useful. (Oracle actually has this problem, you frequently have to add WHERE
col IS NOT NULL" in order to let it use an index.)
--
greg