为了账号安全,请及时绑定邮箱和手机立即绑定

MySQL 删除数据库中重复数据方法小结

标签:
MySQL

刚开始,根据我的想法,这个很简单嘛,上sql语句

?

1delete from zqzrdp where tel in (select min(dpxx_id) from zqzrdp group by tel having count(tel)>1);

执行,报错!!~!~

异常意为:你不能指定目标表的更新在FROM子句。傻了,MySQL 这样写,不行,让人郁闷。

难倒只能分步操作,蛋疼

以下是网友写的,同样是坑爹的代码,我机器上运行不了。

1. 查询需要删除的记录,会保留一条记录。

?

1select a.id,a.subject,a.RECEIVER from test1 a left join (select c.subject,c.RECEIVER ,max(c.id) as bid from test1 c where status=0 GROUP BY RECEIVER,SUBJECT having count(1) >1) b on a.id< b.bid where a.subject=b.subject and a.RECEIVER = b.RECEIVER and a.id < b.bid

2. 删除重复记录,只保留一条记录。注意,subject,RECEIVER 要索引,否则会很慢的。

?

1delete a from test1 a, (select c.subject,c.RECEIVER ,max(c.id) as bid from test1 c where status=0 GROUP BY RECEIVER,SUBJECT having count(1) >1) b where a.subject=b.subject and a.RECEIVER = b.RECEIVER and a.id < b.bid;

3. 查找表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断

?

1select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)

4. 删除表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断,只留有rowid最小的记录

?

1delete from people where peopleId in (select peopleId from people group by peopleId  having count(peopleId) > 1) and rowid not in (select min(rowid) from people group by peopleId having count(peopleId )>1)

5.删除表中多余的重复记录(多个字段),只留有rowid最小的记录

?

1delete from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)


看来想偷懒使用一句命令完成这个事好像不太显示,还是老老实实的分步处理吧,思路先建立复制一个临时表,然后对比临时表内的数据,删除主表里的数据

?

123456789alter table tableName add autoID int auto_increment not null;  create table tmp select min(autoID) as autoID from tableName group by Name,Address;  create table tmp2 select tableName.* from tableName,tmp where tableName.autoID = tmp.autoID;  drop table tableName;  rename table tmp2 to tableName;
点击查看更多内容
TA 点赞

若觉得本文不错,就分享一下吧!

评论

作者其他优质文章

正在加载中
  • 推荐
  • 评论
  • 收藏
  • 共同学习,写下你的评论
感谢您的支持,我会继续努力的~
扫码打赏,你说多少就多少
赞赏金额会直接到老师账户
支付方式
打开微信扫一扫,即可进行扫码打赏哦
今天注册有机会得

100积分直接送

付费专栏免费学

大额优惠券免费领

立即参与 放弃机会
意见反馈 帮助中心 APP下载
官方微信

举报

0/150
提交
取消