MySQL stored procedure return value - mysql

Question

I have to create an SP that returns a value if it's valid or not. But it doesn't return anything and I don't know, why?
CREATE DEFINER=`root`#`localhost` PROCEDURE `validar_egreso`(
IN codigo_producto VARCHAR(100),
IN cantidad INT,
OUT valido INT(11)
)
BEGIN
DECLARE resta INT(11);
SET resta = 0;
SELECT (s.stock - cantidad) INTO resta
FROM stock AS s
WHERE codigo_producto = s.codigo;
IF (resta > s.stock_minimo) THEN
SET valido = 1;
ELSE
SET valido = -1;
END IF;
SELECT valido;
END

Answer 1

You have done the stored procedure correctly but I think you have not referenced the valido variable properly. I was looking at some examples and they have put an # symbol before the parameter like this #Valido
This statement SELECT valido; should be like this SELECT #valido;
Look at this link mysql stored-procedure: out parameter. Notice the solution with 7 upvotes. He has reference the parameter with an # sign, hence I suggested you add an # sign before your parameter valido
I hope that works for you. if it does vote up and mark it as the answer. If not, tell me.

Answer 2

Add:
DELIMITER at the beginning and end of the SP.
DROP PROCEDURE IF EXISTS validar_egreso; at the beginning
When calling the SP, use #variableName.
This works for me. (I modified some part of your script so ANYONE can run it with out having your tables).
DROP PROCEDURE IF EXISTS `validar_egreso`;
DELIMITER $$
CREATE DEFINER='root'#'localhost' PROCEDURE `validar_egreso` (
IN codigo_producto VARCHAR(100),
IN cantidad INT,
OUT valido INT(11)
)
BEGIN
DECLARE resta INT;
SET resta = 0;
SELECT (codigo_producto - cantidad) INTO resta;
IF(resta > 1) THEN
SET valido = 1;
ELSE
SET valido = -1;
END IF;
SELECT valido;
END $$
DELIMITER ;
-- execute the stored procedure
CALL validar_egreso(4, 1, #val);
-- display the result
select #val;

Answer 3

Update your SP and handle exception in it using declare handler with get diagnostics so that you will know if there is an exception.
e.g.
CREATE DEFINER=`root`#`localhost` PROCEDURE `validar_egreso`(
IN codigo_producto VARCHAR(100),
IN cantidad INT,
OUT valido INT(11)
)
BEGIN
DECLARE EXIT HANDLER FOR SQLEXCEPTION
BEGIN
GET DIAGNOSTICS CONDITION 1
#p1 = RETURNED_SQLSTATE, #p2 = MESSAGE_TEXT;
SELECT #p1, #p2;
END
DECLARE resta INT(11);
SET resta = 0;
SELECT (s.stock - cantidad) INTO resta
FROM stock AS s
WHERE codigo_producto = s.codigo;
IF (resta > s.stock_minimo) THEN
SET valido = 1;
ELSE
SET valido = -1;
END IF;
SELECT valido;
END