数据库|mysql教程
查询,重复,记录,删除,方法,大全
数据库-mysql教程
旅游网asp源码,查看ubuntu资源利用,爬虫接口响应失败,php pushkit,seo大神分享lzw
查找所有重复标题的记录: ? 1 SELECT * FROM t_info a WHERE ((SELECT COUNT(*) FROM t_info WHERE Title = a.Title) 1) ORDER BY Title DESC A、查找重复记录 1、查找全部重复记录 ? 1 Select * From 表 Where 重复字段 In (Select 重复字段 From 表 Grou
网点分布查询系统源码,vscode怎么添加服务器,ubuntu吃cpu,tomcat插件下载教程,爬虫 语义分析,php 在线书签,关键词挖掘平台seo顾问lzw
手机留言板php源码,vscode修改git用户,清除ubuntu密码,tomcat0day,SQLITE下载电视剧资源,荣耀手机主题壁纸爬虫游戏,php 获取内网ip,seo项目优化工具,智睿政府网站管理系统,网页作品展示模板lzw
查找所有重复标题的记录:
?
1
SELECT * FROM t_info a WHERE ((SELECT COUNT(*) FROM t_info WHERE Title = a.Title) > 1) ORDER BY Title DESC
A、查找重复记录
1、查找全部重复记录
?
1
Select * From 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)
2、过滤重复记录(只显示一条)
?
1
Select * From HZT Where ID In (Select Max(ID) From HZT Group By Title)
注:此处显示ID最大一条记录
B、删除重复记录
1、删除全部重复记录(慎用)
?
1
Delete 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)
2、保留一条(这个应该是大多数人所需要的 ^_^)
?
1
Delete HZT Where ID Not In (Select Max(ID) From HZT Group By Title)
注:此处保留ID最大一条记录
C、举例
1、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
?
1
select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
2、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
?
1
2
delete 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)
3、查找表中多余的重复记录(多个字段)
?
1
select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
4、删除表中多余的重复记录(多个字段),只留有rowid最小的记录
?
1
2
delete 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)
5、查找表中多余的重复记录(多个字段),不包含rowid最小的记录
?
1
2
select * 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)
D、补充
有两个以上的重复记录,一是完全重复的记录,也即所有字段均重复的记录,二是部分关键字段重复的记录,比如Name字段重复,而其他字段不一定重复或都重复可以忽略。
1、对于第一种重复,比较容易解决,,使用
?
1
select distinct * from tableName
就可以得到无重复记录的结果集。
如果该表需要删除重复的记录(重复记录保留1条),可以按以下方法删除
?
1
2
3
4
select distinct * into #Tmp from tableName
drop table tableName
select * into tableName from #Tmp
drop table #Tmp
发生这种重复的原因是表设计不周产生的,增加唯一索引列即可解决。
2、这类重复问题通常要求保留重复记录中的第一条记录,操作方法如下
假设有重复的字段为Name,Address,要求得到这两个字段唯一的结果集
?
1
2
3
select identity(int,1,1) as autoID, * into #Tmp from tableName
select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID
select * from #Tmp where autoID in(select autoID from #tmp2)