An instance of using a cursor in an mysql stored procedure

DELIMITER $$
DROP PROCEDURE IF EXISTS getUserInfo $$
CREATE PROCEDURE getUserInfo(in date_day datetime)
-- 
--  The instance 
-- MYSQL Stored procedure name: getUserInfo
--  Parameters as follows: date_day The date format :2008-03-08
--
    BEGIN
declare _userName varchar(12); --  The user name 
declare _chinese int ; --  Chinese language and literature 
declare _math int ;    --  mathematics 
declare done int;
--  Define the cursor 
DECLARE rs_cursor CURSOR FOR SELECT username,chinese,math from userInfo where datediff(createDate, date_day)=0;
DECLARE CONTINUE HANDLER FOR NOT FOUND SET done=1;
--  Get yesterday's date 
if date_day is null then
   set date_day = date_add(now(),interval -1 day);
end if;
open rs_cursor; 
cursor_loop:loop
   FETCH rs_cursor into _userName, _chinese, _math; --  Take the data 

   if done=1 then
    leave cursor_loop;
   end if;
--  Update the table 
update infoSum set total=_chinese+_math where UserName=_userName;
end loop cursor_loop;
close rs_cursor;
    END$$
DELIMITER ;