aggregate of an empty result set

Question

I would like the aggregates of an empty result set to be 0. I have tried the following:

SELECT SUM(COALESCE(capacity, 0))
  FROM objects
 WHERE null IS NOT NULL;         


        

Answer 1

Although this post is very old, but i would like to update what I use in such cases

SELECT NVL(SUM(NVL(capacity, 0)),0)
FROM objects
WHERE false;

Here external NVL avoids the cases when there is no row in the result set. Inner NVL is used for null column values, consider the case of (1 + null) and it will result in null. So inner NVL is also necessary other wise in alternate set default value 0 to the column.