MySQL stores procedure cannot add values - mysql

Question

DELIMITER $$
CREATE PROCEDURE GetCustomerLevel(p_barcode int)
BEGIN
DECLARE q1 int;
DECLARE q2 int;
DECLARE q3 int;
DECLARE total int;
SET total :=0;
SELECT sum(adjustment_quantity) INTO q1 FROM adjustment_inventory WHERE item_barcode = p_barcode group by adjustment_quantity;
SELECT sum(opening_stock) INTO q2 FROM openingstock
WHERE item_barcode = p_barcode group by opening_stock;
SELECT sum(inwardquantity) INTO q3
FROM inwardmaster WHERE item_barcode = p_barcode group by inwardquantity;
IF q1 IS NULL THEN
SET q1 := 0;
END IF;
IF q2 IS NULL THEN
SET q2 := 0;
END IF;
IF q3 IS NULL THEN
SET q3 := 0;
END IF;
SELECT q1;
SELECT q2;
SELECT q3;
SELECT q1+q2+q3;
END$$
It's return wrong answer everytime. For example q1=100 q2=200 q3=100 its return 100

Answer 1

you dont need to use stored procedure for this
set #barcode = '1234';
select
coalesce((
SELECT sum(coalesce(adjustment_quantity,0))
FROM adjustment_inventory
WHERE item_barcode = #p_barcode
),0) +
coalesce((
SELECT sum(opening_stock)
FROM openingstock
WHERE item_barcode = #p_barcode
), 0) +
coalesce((
SELECT
sum(coalesce(inwardquantity,0))
FROM inwardmaster WHERE item_barcode = #p_barcode
), 0) res
From Dual
;
If you really want to use procedure then check the code below
DELIMITER $$
CREATE PROCEDURE GetCustomerLevel(p_barcode int)
BEGIN
DECLARE q1 int;
DECLARE q2 int;
DECLARE q3 int;
DECLARE total int;
SET total :=0;
SELECT coalesce(sum(adjustment_quantity), 0) INTO q1 FROM adjustment_inventory WHERE item_barcode = p_barcode;
SELECT coalesce(sum(opening_stock), 0) INTO q2 FROM openingstockWHERE item_barcode = p_barcode;
SELECT coalesce(sum(inwardquantity), 0) INTO q3 FROM inwardmaster WHERE item_barcode = p_barcode;
SELECT q1;
SELECT q2;
SELECT q3;
set total = q1+q2+q3;
SELECT total;
END$$