There are no qualifying records, and the SUM function returns NULL. Returns 0 instead of NULL

But in most cases, we want it to return 0 instead of NULL if the condition record is not met, so we can use the following method, for example:

SELECT COALESCE (SUM(isnull(filed,00as[filed1] from table1

Okay, so you don't have to bother with the case of whether the return result is null.

The COALESCE function means returning the first empty value in the argument list, which allows multiple arguments to be passed in, which is also a standard function in SQL.

There are no qualifying records, and the SUM function returns NULL. Returns 0 instead of NULL