www.fltk.net > mysql 怎么删除重复的数据保留一条数据

mysql 怎么删除重复的数据保留一条数据

这个需要分情况。 1,你的数据库表中有主键,且主键上面的数据为唯一值。也就是没有重复值。 那么你在删除的时候,将这个唯一值作为条件进行删除。 如: delete from [表名] where id=1 2.所有的数据相同,那么你只能打开数据表,手工选定其中某一...

delete from temp where id in (select id from (select max(id) as id,count(url) as count from temp group by url having count >1 order by count desc) as tab )

只能用变通的办法 假设表有N1,N2,N3三个字段,都是INT类型,表名是NUMBER,执行如下语句: DECLARE @TB TABLE (N1 INT,N2 INT,N3 INT); INSERT INTO @TB SELECT TOP 1 * FROM NUMBER; DELETE NUMBER; INSERT INTO NUMBER SELECT * FROM @TB; SELE...

delete from mygame_article where id not in ( select max(id) from mygame_article group by title);

delete from `mygame_article` where title in (select title from `mygame_article` group by id having count(title) > 1) and id not in (select max(id) from `mygame_article` group by title having count(title) > 1); 随手写了个,前半...

案例: id 姓名 课程名称 分数 1 张三 数学 69 2 李四 数学 89 3 张三 数学 69 删除除了自动编号不同,其他都相同的学生冗余信息 ------------------------------------------------------------------------------------------------------ 按常...

在语句中加个关键字就行了; select distinct domain from 表名; 查询的结果中就已经自动去重了

delete from dep where id not in ( select * from (select max(id) from dep group by id having count(id )>1) b);

MySQL查询重复字段,及删除重复记录的方法 数据库中有个大表,需要查找其中的名字有重复的记录id,以便比较。如果仅仅是查找数据库中name不重复的字段,很容易: SELECT min(`id`),`name` FROM `table` GROUP BY `name`; 但是这样并不能得到说有重...

select distinct question_type from question

网站地图

All rights reserved Powered by www.fltk.net

copyright ©right 2010-2021。
www.fltk.net内容来自网络,如有侵犯请联系客服。zhit325@qq.com