Re: Finding null values in a large table

Tim Dry wrote:
>
> 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

create index the_nulls on the_table (
  decode(col,null,-1,null))

select ..
from the_table
where decode(col,null,-1,null) = -1

or similar. Obviously the idea is that you don't have lots and lots of nulls - otherwise the full scan will be better anyway

hth
connor

-- 
==============================
Connor McDonald

http://www.oracledba.co.uk

"Some days you're the pigeon, some days you're the statue..."