รบกวนด้วยครับ เกี่ยวกับ store procedure auto increment id

SELECT CONCAT('DEP',LPAD(IFNULL(MAX(CONVERT(REPLACE(DepCod,'DEP',''),UNSIGNED))+1,1),5,'0'))

DELIMITER $$

USE `abc`$$

DROP PROCEDURE IF EXISTS `fn_addCategory`$$

CREATE DEFINER=`root`@`localhost` PROCEDURE `fn_addCategory`(IN `p_department` VARCHAR(100), IN `p_eDepartment` VARCHAR(100))
BEGIN
	DECLARE l_dep CHAR(10);
	
	DECLARE l_type CHAR(10);
	SET l_type = 'DEP';

	SET l_dep = "SELECT CONCAT('DEP',LPAD(IFNULL(MAX(CONVERT(REPLACE(DepCod,'DEP',''),UNSIGNED))+1,1),5,'0'))";
	
	

	INSERT INTO depmst(DepCod,DepLocNam,DepEngNam,DepTyp)
	VALUES (l_dep , p_department, p_eDepartment, l_type);
END$$

DELIMITER ;