DELIMITER $$
CREATE DEFINER=`root`@`localhost` FUNCTION `STRINGDECODE`(STR TEXT CHARSET utf8, DELIM_CHAR TEXT CHARSET utf8) RETURNS text CHARSET utf8
    DETERMINISTIC
BEGIN
        DECLARE STR_LENGTH INT UNSIGNED;
    DECLARE STR_INDEX INT UNSIGNED;
    DECLARE STR_COUNTER INT UNSIGNED;
    DECLARE STR_CURRENT TEXT CHARSET utf8;
    DECLARE STR_RESULT TEXT CHARSET utf8;

        SET STR_LENGTH = JSON_LENGTH(STR);
    SET STR_COUNTER = STR_LENGTH;
    SET STR_RESULT = '';

        WHILE STR_COUNTER > 0 DO
                SET STR_INDEX = STR_LENGTH - STR_COUNTER;

                SET STR_CURRENT = JSON_UNQUOTE(JSON_EXTRACT(STR, CONCAT('$[', STR_INDEX, ']')));

                SET STR_RESULT = CONCAT(STR_RESULT, STR_CURRENT);

                IF STR_COUNTER > 1 THEN
            SET STR_RESULT = CONCAT(STR_RESULT, DELIM_CHAR);
        END IF;

                SET STR_COUNTER = STR_COUNTER - 1;
    END WHILE;

    RETURN STR_RESULT;
END$$
DELIMITER ;