set语句中的MySQL脚本

这就是我创造的:

创建函数change_int(colres VARCHAR(500))返回int(11)
开始

    DECLARE res int(11);
    DECLARE leng int(11);
    DECLARE newres int(11);
    DECLARE mult int(11);
    DECLARE temp1 int(11);
    DECLARE temp2 int(11);  

SET res = CAST(colres AS UNSIGNED);
SET leng = CHAR_LENGTH(CAST( colres AS CHAR)); 
SET newres = 0;
SET mult = 1;
SET temp1 = 0;
SET temp2 = 0;


WHILE (res > 0) DO

    SET temp1 = MOD(res , 10 );
    SET res = (res DIV 10);
    SET temp2 = MOD(res , 10 );
    SET newres = (newres +((temp1 + temp2 ) * mult));       
    SET mult = mult*10;
END WHILE;
SET newres = SUBSTRING (newres, 1, leng );
RETURN newres;  
END $$
DELIMITER ;

但当我在第6行尝试运行它时,会出现错误:

#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ''res' = CAST(colres AS CHAR)' at line 6

 #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SET newres = SUBSTRING (newres, 1, leng );
    RETURN newres;    
    END' at line 27

格雷特:现在它起作用了。 但我无法唤起她:

SHOW FUNCTION STATUS;

它是存在的。

当我尝试这样运行它时:

UPDATE `table` SET `col1` = function_name(`col1`);

UPDATE `table` SET `col1` = db.function_name(`col1`);

不走运。