IF ELSE with NULL values mysql - mysql

Question

im having problems creating a function that must return the amount of goals of a team as a home and away
First it sums all local goals, and then it sums all visitor goals, and saves into variables, but the problem is, i want to know what can i do if there is NO data, i mean, what can i do when it returns NULL, i tried with IF ELSE but still not working, here is the code:
CREATE DEFINER=`root`#`localhost` FUNCTION `vgoles`(`veq` int) RETURNS int(11)
BEGIN
#Routine body goes here...
DECLARE vgloc INT;
DECLARE vgvis INT;
DECLARE vgoles INT;
SELECT SUM(gloc) INTO #vgloc FROM partidos WHERE eqloc=#veq;
SELECT SUM(gvis) INTO #vgvis FROM partidos WHERE eqvis=#veq;
IF #vgloc = NULL THEN
SET #vgloc = 0;
END IF;
IF #vgvis = NULL THEN
SET #vgvis = 0;
END IF;
SET #vgoles=#vgloc+#vgvis;
RETURN #vgoles;
END
Thanks and have a nice day

Answer 1

The IF #vgloc = NULL THEN does not work as you expect because you can't check NULL with equality (=). NULL is a special value that is not equal to anything, not even to itself.
SELECT (3 = NULL) --yields--> NULL
SELECT NOT (3 = NULL) --yields--> NULL
SELECT (NULL = NULL) --yields--> NULL
SELECT (NULL <> NULL) --yields--> NULL
SELECT (NULL IS NULL) --yields--> TRUE
To check for NULL value, you need: IF #vgloc IS NULL THEN.
But you can also use COALESCE() function for further simplicity:
SELECT COALESCE(SUM(gloc),0) INTO #vgloc FROM partidos WHERE eqloc=#veq;
SELECT COALESCE(SUM(gvis),0) INTO #vgvis FROM partidos WHERE eqvis=#veq;