sql语句查询重复的数据
查找所有重复标题的记录：
1 2 3 4 5 6 | SELECT *FROM t_info aWHERE ((SELECT COUNT(*)FROM t_infoWHERE Title = a.Title) > 1)ORDER BY Title DESC |
一。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
二。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
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 2 | select * from peoplewhere 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 3 | delete from peoplewhere 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 2 | select * from vitae awhere (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 3 | delete from vitae awhere (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 3 | select * from vitae awhere (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) |
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 tableNamedrop table tableNameselect * into tableName from #Tmpdrop 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 tableNameselect min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoIDselect * from #Tmp where autoID in(select autoID from #tmp2) |
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