This sql script can be used to keep cumulative stock balance in stockdiary table.

Execute below script once in mySQL.

ALTER TABLE STOCKDIARY ADD COLUMN STOCKBALANCE INT;
DROP PROCEDURE if exists updateStockBalance;
DELIMITER $$
CREATE PROCEDURE updateStockBalance()
BEGIN
 DECLARE done INT DEFAULT FALSE;
    DECLARE o_id VARCHAR(255);
    DECLARE balance INT;
    DECLARE cur1 CURSOR FOR SELECT ID FROM PRODUCTS;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
    OPEN cur1;
    read_loop: LOOP
    FETCH cur1 INTO o_id;
    SET @balance = 0;
    SET @pid = o_id;
    UPDATE STOCKDIARY  SET STOCKBALANCE=@balance:=@balance + UNITS WHERE PRODUCT LIKE @pid AND STOCKBALANCE IS NULL ORDER BY DATENEW;
    IF done THEN
      LEAVE read_loop;
    END IF;
    END LOOP;
    CLOSE cur1;
    END$$
DELIMITER ;

Schedule below script to keep the stockbalance column updated:
CALL updateStockBalance();

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