Looney, Jason wrote: > My understanding was in the past count(*) returned a count of all non-null > rows, where count(1) (or any constant) returned a count of all rows. I just > verified this with 10g and this is not the case. The performance difference > was to perform a full table scan, instead of counting leaf blocks in a > primary key index or something like that. So maybe this was true in 6 or 7? > > [...] For what it's worth, my recollection is the same, except I think it was the other way around -- count('x') (based on unique index) would return only non-nulls, because of the way regular indexes handle nulls, while count(*) (full table scan) would return all rows. I couldn't quickly reproduce the behavior in 10g either, and didn't bother with an older version. -- Mark Bole http://www.bincomputing.com -- //www.freelists.org/webpage/oracle-l