oracle怎么查重复,Oracle 查询重复数据

在oracle数据库中,怎样查询出只有一个字段的表的重复数据?

方法一:可以通过group by 进行分组。\x0d\x0asql:select username,count(username) from tablename grop by username;\x0d\x0a解释:以上sql就是通过分组函数读取出tablename表中username的值和每个不同值的统计个数。\x0d\x0a方法二:可以通过distinct函数 进行去重查询。\x0d\x0asql:select distinct username from tablename\x0d\x0a解释:本sql就是查询出所有的tablename表中的username值(不重复)。

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Oracle如何查询相同的数据?

如果你只要id重复的,是\x0d\x0aselect * from 表 where id in (select id from 表 group by id having count(*)1) \x0d\x0a \x0d\x0a如果你要所有字段都完全一样的重复记录的话,就是\x0d\x0aselect * from 表 where id in (select id from 表 group by id,name,age having count(*)1)

oracle如何查重复数据并显示出来?

SELECT *\x0d\x0aFROM t_info a\x0d\x0aWHERE ((SELECT COUNT(*)\x0d\x0a FROM t_info\x0d\x0a WHERE Title = a.Title) 1)\x0d\x0aORDER BY Title DESC\x0d\x0a一。查找重复记录\x0d\x0a1。查找全部重复记录\x0d\x0aSelect * From 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)1)\x0d\x0a2。过滤重复记录(只显示一条)\x0d\x0aSelect * From HZT Where ID In (Select Max(ID) From HZT Group By Title)\x0d\x0a注:此处显示ID最大一条记录\x0d\x0a二。删除重复记录\x0d\x0a\x0d\x0a1。删除全部重复记录(慎用)\x0d\x0aDelete 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)1)\x0d\x0a2。保留一条(这个应该是大多数人所需要的 ^_^)\x0d\x0aDelete HZT Where ID Not In (Select Max(ID) From HZT Group By Title)\x0d\x0a注:此处保留ID最大一条记录\x0d\x0a1、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\x0d\x0aselect * from people\x0d\x0awhere peopleId in (select peopleId from people group by peopleId having count(peopleId) 1)\x0d\x0a \x0d\x0a2、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\x0d\x0adelete from people\x0d\x0awhere peopleId in (select peopleId from people group by peopleId having count(peopleId) 1)\x0d\x0aand rowid not in (select min(rowid) from people group by peopleId having count(peopleId )1)\x0d\x0a \x0d\x0a3、查找表中多余的重复记录(多个字段)\x0d\x0aselect * from vitae a\x0d\x0awhere (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) 1)\x0d\x0a \x0d\x0a4、删除表中多余的重复记录(多个字段),只留有rowid最小的记录\x0d\x0adelete from vitae a\x0d\x0awhere (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) 1)\x0d\x0aand rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)1)\x0d\x0a \x0d\x0a5、查找表中多余的重复记录(多个字段),不包含rowid最小的记录\x0d\x0aselect * from vitae a\x0d\x0awhere (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) 1)\x0d\x0aand rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)1)\x0d\x0a\x0d\x0a补充:\x0d\x0a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。\x0d\x0a \x0d\x0a1、对于第一种重复,比较容易解决,使用\x0d\x0aselect distinct * from tableName\x0d\x0a \x0d\x0a就可以得到无重复记录的结果集。\x0d\x0a \x0d\x0a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\x0d\x0aselect distinct * into #Tmp from tableName\x0d\x0adrop table tableName\x0d\x0aselect * into tableName from #Tmp\x0d\x0adrop table #Tmp\x0d\x0a \x0d\x0a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。\x0d\x0a \x0d\x0a2、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\x0d\x0a \x0d\x0a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\x0d\x0aselect identity(int,1,1) as autoID, * into #Tmp from tableName\x0d\x0aselect min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID\x0d\x0aselect * from #Tmp where autoID in(select autoID from #tmp2)


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