mysql 删除重复项sql语句

mysql 删除重复项sql语句

我的sql 代码：SELECT v.iId, v.iNo, v.vTitle, l.vTitle AS lesson, h.cDate FROM user_video_history h
 JOIN biz_video v ON h.iVideoId=v.iId JOIN biz_lesson l ON v.iLessonId=l.iId
 WHERE h.vUserCode='1000563' GROUP BY vTitle , cDate DESC  LIMIT 0, 20

首先我对日期进行了倒序，显示最新的，但是我想删除重复的题目，试了很多办法，没成功

delete  A
from tb A,tb B
where A.ino=B.ino and A.vtitle=B.vtitle and A.lesson=B.lesson and A.cDate>B.cDate;

select *
from (
SELECT v.iId, v.iNo, v.vTitle, l.vTitle AS lesson, h.cDate FROM user_video_history h
 JOIN biz_video v ON h.iVideoId=v.iId JOIN biz_lesson l ON v.iLessonId=l.iId
 WHERE h.vUserCode='1000563' GROUP BY vTitle , cDate DESC  LIMIT 0, 20
) t group by vTitle