今天在写存储过程，给其他表插入数据时，发现，我游标取出来的数据明明只有一条，但是在循环过程中，却发现插入了两条数据。下面是代码

 

BEGIN

#Routine body goes here...

DECLARE event_content1 VARCHAR(255);

DECLARE event_id1 INT;

DECLARE event_name VARCHAR(255);

DECLARE start_time1 TIMESTAMP;

DECLARE end_time1 TIMESTAMP;

DECLARE  result_counts1 INT;

DECLARE High_result_time1 TIMESTAMP;

DECLARE high_result_counts1 INT;

DECLARE start_result_time1 TIMESTAMP;

DECLARE start_result_name1 text;

DECLARE reposts_counts1 INT;

DECLARE comments_counts1 INT;

DECLARE attitude_counts1 INT;

DECLARE done INT DEFAULT FALSE;

DECLARE  cur cursor for SELECT id,event_content,create_time,finish_time FROM t_public_concern_event WHERE `status` = 1  ;

DECLARE CONTINUE HANDLER FOR NOT FOUND SET done = TRUE;

OPEN cur;

TRUNCATE TABLE event_preview;

read_loop:LOOP

    

if done THEN

            LEAVE read_loop;

            END IF;

# 游标 获取事件列表

FETCH cur INTO event_id1,event_content1,start_time1,end_time1;

# 获取事件相关结果数

select COUNT(1) INTO result_counts1 from t_public_opinion_realtime_weibo WHERE title= event_content1;

# 获取事件最多的某一天,以及总数

SELECT counts,create_time into high_result_counts1,High_result_time1  FROM (select COUNT(1) as counts,DATE_FORMAT(create_time,"%Y-%m-%d") as create_time FROM t_public_opinion_realtime_weibo WHERE title=event_content1 GROUP BY DATE_FORMAT(create_time,"%Y-%m-%d")) as a WHERE a.counts = (SELECT MAX(counts) from (select COUNT(1) as counts,DATE_FORMAT(create_time,"%Y-%m-%d") FROM t_public_opinion_realtime_weibo WHERE title=event_content1 GROUP BY DATE_FORMAT(create_time,"%Y-%m-%d")) as b);

# 获取事件源头

SELECT text,create_time into start_result_name1,start_result_time1 from t_public_opinion_realtime_weibo WHERE title = event_content1 ORDER BY create_time LIMIT 1;

# 总转发 总点赞，总评论

select SUM(reposts_count) ,SUM(comments_count) , SUM(attitudes_count) INTO reposts_counts1,comments_counts1,attitude_counts1  from t_public_opinion_realtime_weibo WHERE title = event_content1;   

INSERT INTO event_preview (event_id,start_time,end_time,result_counts,High_result_time,high_result_counts,start_result_time,start_result_name,reposts_counts,comments_counts,attitude_counts)VALUES(event_id1,start_time1,end_time1,result_counts1,High_result_time1,high_result_counts1,start_result_time1,start_result_name1,reposts_counts1,comments_counts1,attitude_counts1);

END LOOP;

CLOSE cur;

END

结果造成了游标取出来是一条，但是插入却出现两条：

 

 

检查后发现没有错， 后来修改，查找，发现是Fetch  游标的位置不对，造成的。

 

正确的写法是在判断游标为空 也就是 IF 之前 fetch 游标：

 

OPEN cur;

TRUNCATE TABLE event_preview;

read_loop:LOOP

    # 在if 之前fetch 游标

    FETCH cur INTO event_id1,event_content1,start_time1,end_time1;

if done THEN

            LEAVE read_loop;

            END IF;

# 其他操作

        。。。。。。。

这样下来就没错了。