DELIMITER $$
CREATE OR REPLACE DEFINER=`vn`@`localhost` PROCEDURE `vn`.`nextShelvingCodeMake`()
BEGIN

	DECLARE newShelving VARCHAR(3);
    DECLARE vCode VARCHAR(3);
    
    SELECT MAX(code) INTO vCode
		FROM vn.shelving
        WHERE isPrinted = FALSE;
	
    SET @a1 := ASCII(MID(vCode,1,1));
    SET @a2 := ASCII(MID(vCode,2,1));
    SET @a3 := ASCII(MID(vCode,3,1)) + 1;
    
    IF @a3 > 90 THEN
    
		SET @a3 = 65;
        SET @a2 = @a2 + 1;
        
        IF @a2 > 90 THEN
        
			SET @a2 = 65;
            SET @a1 = @a1 + 1;
            
            IF @a1 > 90 THEN
            
				SET @a1 = 65;
            
            END IF;
        
        END IF;
    
    END IF;

	SET newShelving = CHAR(@a1,@a2,@a3 USING utf8);
    
	INSERT INTO vn.shelving(code) VALUES(newShelving);

END$$
DELIMITER ;