On Wed, May 28, 2003 at 23:43:19 -0700,
Vincent Hikida <vhikida@inreach.com> wrote:
>
> That is
>
> SELECT SUM(numvar) FROM tablex
>
> Will treat any numvar which are null as if they were a zero. However, the
> following will not treat it as zero but non-existent.
Aggragates (except for count(*)) will skip any row for which the expression
is null. For sum() that turns out to be equivalent to treating the number
as zero because of the way math works. But the function isn't actually
treating nulls as zeros.