David Johnston <polobo@yahoo.com> writes:
> On Aug 31, 2012, at 19:14, Thalis Kalfigkopoulos <tkalfigo@gmail.com> wrote:
>> This didn't work as expected (the NULL's persisted):
>> ...CASE sum(foo) WHEN NULL THEN 0 ELSE sum(foo) END...
> Guessing this form effectively evaluates to
> WHEN sum(foo) = NULL instead of IS NULL and thus the wrong answer:
Yeah, I think that's right.
> That said you might want to try
> SUM(COALESCE(foo, 0))
Actually I'd go with "COALESCE(SUM(foo), 0)" since that requires only
one COALESCE operation, not one per row.
regards, tom lane