On Aug 31, 2012, at 22:49, Tom Lane <t...@sss.pgh.pa.us> wrote: > David Johnston <pol...@yahoo.com> writes: >> On Aug 31, 2012, at 21:52, Tom Lane <t...@sss.pgh.pa.us> wrote: >>> David Johnston <pol...@yahoo.com> writes: >>>> 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. > >> These are not equivalent if some values of foo are not-null and you want the >> sum of all non-null values while replacing any nulls with zero. So the >> decision depends on what and why you are summing. > > But SUM() ignores input nulls, so I think they really are equivalent. > I agree that in a lot of other cases (for instance MAX), you'd have to > think harder about which behavior you wanted. >
This I did not know/recall, was assuming nulls poisoned the result. David J. -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
