Just for information: Oracle returns NULL's in both cases: for SUM() and for AVG().
I checked it for ver. 8.1.7 and 9.2.0 --- "D. Richard Hipp" <[EMAIL PROTECTED]> wrote: > On Thu, 2005-09-08 at 10:24 -0700, Will Leshner > wrote: > > Say I have a column called 'b' in a table called > 'test' and every > > field in 'b' has a NULL value. What is the > expected behavior of the > > following query: > > > > SELECT SUM(b) FROM TEST; > > > > I guess I'm thinking I'll get back NULL. Instead I > get 0 (or, in the > > 3.2.5 code, 0.0). > > > > SUM ignores NULLs. So if it ignores everything, it > returns the > sum of nothing, which is 0. (Not the 0.0 issue is > fixed in CVS HEAD.) > > > On the other hand, the following query does return > NULL: > > > > SELECT AVG(b) FROM TEST; > > > > AVG is implemented as SUM/COUNT. But the count is > zero. So > you get a NULL. > -- > D. Richard Hipp <[EMAIL PROTECTED]> > >
