SQL if not null update

Question

I have this query

UPDATE users SET username = Param1,email = Param2,PASSWORD = Param3 WHERE id = Param4;

this is updating my user row, but

Answer 1

UPDATE users 
SET username = Param1,
email = Param2,
PASSWORD = Param3 
WHERE id = Param4 AND (ISNULL(email,'') != '' OR ISNULL(PASSWORD, '') != '');