DELETE m FROM test.`tb1` m
JOIN
(SELECT id,val FROM test.`tb1` GROUP BY id,val HAVING COUNT(*)>1 ) n
ON m.`id` = n.id AND m.`val`= n.val;
JOIN
(SELECT id,val FROM test.`tb1` GROUP BY id,val HAVING COUNT(*)>1 ) n
ON m.`id` = n.id AND m.`val`= n.val;
select *
from tbname A
where not exists (select 1 from tbname where A.username=username and A.contentText=contentText A.id>id);drop table tbname;
alter table tbname1 rename tbname;
这些字段,求详细呀你那段语句我不知道怎么修改
2 2
3 4
3 4
把 第二行和第三行 都删掉
你的需求是这样?
JOIN
(SELECT id,val FROM test.`tb1` GROUP BY id,val HAVING COUNT(*)>1 ) n
ON m.`id` = n.id AND m.`val`= n.val ;不是临时表,内存表。。
JOIN
(SELECT id,val FROM test.`tb1` GROUP BY id,val HAVING COUNT(*)>1 ) as n
ON m.`id` = n.id AND m.`val`= n.val ;
JOIN
(SELECT id,val FROM bigdata_comment GROUP BY UserName ,ContentText HAVING COUNT(*)>1 ) as n
ON m.UserName = n.UserName AND m.ContentText=n.ContentText;
JOIN
(SELECT UserName ,ContentText FROM bigdata_comment GROUP BY UserName ,ContentText HAVING COUNT(*)>1 ) as n
ON m.UserName = n.UserName AND m.ContentText=n.ContentText; 你对SQL 完全空白啊
这样的话,用你那个语句的话会把重复的一块删除了只会留下一个dd ff 我要的是删除之后留下的是
dd ff
aa bb
能不能这样啊???
JOIN
(SELECT ID, UserName ,ContentText FROM bigdata_comment GROUP BY UserName ,ContentText HAVING COUNT(*)>1 ) as n
ON m.UserName = n.UserName AND m.ContentText=n.ContentText
where m.ID != n.ID; id 是唯一主键吧,是的话就这个