On 2012-09-01, Chris Angelico <rosuav@xxxxxxxxx> wrote: > On Sat, Sep 1, 2012 at 12:07 PM, David Johnston <polobo@xxxxxxxxx> wrote: >> 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. > > It comes to the same result with SUM though isn't it? no sum over zero rows always returns null. an external coalesce will make the result 0 whilst an internal coalesce will have no effect and NULL will be the result. with t as ( select 1::int as a where false ) select sum(coalesce (a,0)) as inner,coalesce (sum(a),0) as outer from t; -- ⚂⚃ 100% natural -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
