DELIMITER $$
USE `database`$$
DROP TRIGGER /*!50032 IF EXISTS */ `nambah`$$
CREATE
    /*!50017 DEFINER = 'root'@'localhost' */
    TRIGGER `nambah` BEFORE INSERT ON `transactions`
    FOR EACH ROW BEGIN
    DECLARE str_len INT DEFAULT 6; /*jumlah karakter*/
    DECLARE ready INT DEFAULT 0;
    DECLARE rnd_str TEXT;
    WHILE NOT ready DO
        SET rnd_str := LPAD(CONV(FLOOR(RAND()*POW(36,str_len)), 10, 36), str_len, 0);
        IF NOT EXISTS (SELECT * FROM transactions WHERE trans_code = rnd_str) THEN
        SET new.trans_code = rnd_str;
        SET ready := 1;
        END IF;
    END WHILE;
    END;
$$
DELIMITER ;