mysql存储过程中游标如何遍历

CREATE DEFINER=`root`@`%` PROCEDURE `updStatus`()
BEGIN
DECLARE startTime DATETIME;
DECLARE endTime DATETIME;
DECLARE curTime DATETIME;
DECLARE id VARCHAR(36); 
DECLARE estatus VARCHAR(4); 
-- 遍历数据结束标志
 DECLARE done INT DEFAULT FALSE;
 -- 游标
 DECLARE examIds CURSOR FOR SELECT EXAM_ID FROM t_exam WHERE EXAM_STATUS = 1 or EXAM_STATUS = 2;
 -- 将结束标志绑定到游标
 DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;
OPEN examIds; 
 -- 遍历
 read_loop: LOOP
-- 取值 取多个字段
FETCH NEXT from examIds INTO id;
IF done THEN
LEAVE read_loop;
END IF;
SELECT EXAM_STATUS INTO estatus FROM t_exam WHERE EXAM_ID = id ;
IF estatus =1 THEN
SELECT NOW() INTO curTime;
SELECT EXAM_START_TIME INTO startTime from t_exam WHERE EXAM_ID = id ;
SELECT EXAM_END_TIME INTO endTime from t_exam WHERE EXAM_ID = id ;
IF curTime >= startTime AND endTime > curTime THEN
UPDATE t_exam SET EXAM_STATUS = 2 WHERE EXAM_ID = id;
ELSEIF curTime >= endTime THEN
UPDATE t_exam SET EXAM_STATUS = 3 WHERE EXAM_ID = id;
END IF;
ELSE
SELECT NOW() INTO curTime;
SELECT EXAM_END_TIME INTO endTime from t_exam WHERE EXAM_ID = id ;
IF curTime >= endTime THEN
UPDATE t_exam SET EXAM_STATUS = 3 WHERE EXAM_ID = id;
END IF;
END IF;
 END LOOP;
 
 CLOSE examIds;
END