Re: Finding null values in a large table

From: Paul Brewer <paul_at_paul.brewers.org.uk>
Date: Fri, 6 Dec 2002 02:21:36 -0000
Message-ID: <3df0f35f_2@mk-nntp-1.news.uk.worldonline.com>

"Tim Dry" <tldry_at_charter.net> wrote in message news:fad761ad.0212051545.14b89cc7_at_posting.google.com...
> I have a fairly large table (millions of rows) and I would like to be
> able to find rows that have a null value in a particular column. I
> know that regular indexes don't contain null values and thus an index
> on this particular column probably wouldn't help. I believe that
> bitmap indexes include nulls, but bitmap indexes are supposedly
> inefficient when the column is too selective. Are there other
> solutions?
>
> -Tim

Tim,

Not a lot to go on here. If you're using 8i or above, a function based index might be the answer, assuming this a regular requirement. For a one off, I'd bear the pain - a table scan shouldn't be more than (say) 30 seconds, surely? How many millions of rows?

Personally (this may well be blind prejudice, but there has been a problem or three) I am inclined to avoid bitmap indexes.

Regards,
Paul Received on Thu Dec 05 2002 - 20:21:36 CST