MySQL 函数：获取字符串字母部分

BEGIN
DECLARE v_length INT DEFAULT 0;
DECLARE v_Tmp varchar(50) default '';
set v_length=CHAR_LENGTH(Varstring);
WHILE v_length > 0 DO

IF (mid(Varstring,v_length,1) REGEXP '[a-zA-Z]') THEN
set v_Tmp=concat(v_Tmp,mid(Varstring,v_length,1));
END IF;
SET v_length = v_length - 1;
END WHILE;
RETURN REVERSE(v_Tmp);

END

【注：Varstring是传入的参数，通过正则表达式取值】