MySQL [test]> select '1234万美元' + 0 as num;

+------+

| num  |

+------+

| 1234 |

+------+

DELIMITER $$

DROP FUNCTION IF EXISTS `Num_char_extract`$$

CREATE FUNCTION `Num_char_extract`(Varstring VARCHAR(100)CHARSET utf8, flag INT) RETURNS VARCHAR(50) CHARSET utf8

COMMENT '标识 0 提取数字 1 提取字母 2提取数字+字母 3 提取汉字'

BEGIN

    DECLARE len INT DEFAULT 0;

    DECLARE Tmp VARCHAR(100) DEFAULT '';

    SET len=CHAR_LENGTH(Varstring);

    IF flag = 0

    THEN

        WHILE len > 0 DO

        IF MID(Varstring,len,1)REGEXP'[0-9]' THEN

        SET Tmp=CONCAT(Tmp,MID(Varstring,len,1));

        END IF;

        SET len = len - 1;

        END WHILE;

    ELSEIF flag=1

    THEN

        WHILE len > 0 DO

        IF (MID(Varstring,len,1)REGEXP '[a-zA-Z]')

        THEN

        SET Tmp=CONCAT(Tmp,MID(Varstring,len,1));

        END IF;

        SET len = len - 1;

        END WHILE;

    ELSEIF flag=2

    THEN

        WHILE len > 0 DO

        IF ( (MID(Varstring,len,1)REGEXP'[0-9]')

        OR (MID(Varstring,len,1)REGEXP '[a-zA-Z]') )

        THEN

        SET Tmp=CONCAT(Tmp,MID(Varstring,len,1));

        END IF;

        SET len = len - 1;

        END WHILE;

    ELSEIF flag=3

    THEN

        WHILE len > 0 DO

        IF NOT (MID(Varstring,len,1)REGEXP '^[u0391-uFFE5]')

        THEN

        SET Tmp=CONCAT(Tmp,MID(Varstring,len,1));

        END IF;

        SET len = len - 1;

        END WHILE;

    ELSE

        SET Tmp = 'Error: The second paramter should be in (0,1,2,3)';

        RETURN Tmp;

    END IF;

    RETURN REVERSE(Tmp);

    END$$

DELIMITER ;

-- select Num_char_extract('字12段',0);