CODEWITHSUNDEEP
mysqlnullif-statement
Enrique Benitez
Enrique Benitez

Reputation: 679

IF ELSE with NULL values mysql

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

Upvotes: 0

Views: 5680

Answers (1)

ypercubeᵀᴹ
ypercubeᵀᴹ

Reputation: 115530

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;

Upvotes: 4

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