mysql遍历字符串，按ASCII码拼接返回数字

对于按照字符排序，对于排序的结果值需要运算的，可能直接order by (xxx + 0)的形式可能行不通，于是调用函数 to_number(xxx)，可以对于返回数字进行排序

DELIMITER $$

USE `maventest`$$

DROP FUNCTION IF EXISTS `to_number`$$

CREATE DEFINER=`root`@`localhost` FUNCTION `to_number`(NAME VARCHAR(255) CHARSET gbk) RETURNS VARCHAR(4000) CHARSET gbk
BEGIN
    DECLARE mycode INT;
    DECLARE tmp_lcode VARCHAR(2) CHARSET gbk;
    DECLARE lcode INT;
    DECLARE mypy VARCHAR(4000) CHARSET gbk DEFAULT '';
    DECLARE lp INT;
    SET mycode = 0;
    SET lp = 1;
    SET NAME = HEX(NAME);
    WHILE lp < LENGTH(NAME) DO
        SET tmp_lcode = SUBSTRING(NAME, lp, 2);
        SET lcode = CAST(ASCII(UNHEX(tmp_lcode)) AS UNSIGNED);
        IF lcode > 128 THEN
            SET lp = lp + 4;
        ELSE
            SET lp = lp + 2;
        END IF;
        SET mypy = CONCAT(mypy,lcode);
    END WHILE;
    RETURN LOWER(mypy);
END$$

DELIMITER ;