A tip for avoiding null values in aggregate functions in sql

Sometimes the aggreagete functions in SQL returns null value - when the data doesn't meet selection criteria defined in the query.
We can return 0 instead NULL with (ISNULL (column, 0)).

For example:
SELECT
(ISNULL (SUM (salary), 0)) As Total
FROM Salaries
WHERE
UserId=@UserId

Using such statement avoids checking for null values in the code.