SQL重复记录查询的几种方法

      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

      复制代码 代码如下:

      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

      复制代码 代码如下:

      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） 

      复制代码 代码如下:

      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

      复制代码 代码如下:

      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

      复制代码 代码如下:

      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)

      (二)
      比方说
      在A表中存在一个字段“name”，
      而且不同记录之间的“name”值有可能会相同，
      现在就是需要查询出在该表中的各记录之间，“name”值存在重复的项；

      复制代码 代码如下:

      Select Name,Count(*) From A Group By Name Having Count(*) > 1

      如果还查性别也相同大则如下:

      复制代码 代码如下:

      Select Name,sex,Count(*) From A Group By Name,sex Having Count(*) > 1

      (三)
      方法一

      复制代码 代码如下:

      declare @max integer,@id integer
      declare cur_rows cursor local for select 主字段,count(*) from 表名 group by 主字段 having

      count(*) >； 1
      open cur_rows
      fetch cur_rows into @id,@max
      while @@fetch_status=0
      begin
      select @max = @max -1
      set rowcount @max
      delete from 表名 where 主字段 = @id
      fetch cur_rows into @id,@max
      end
      close cur_rows
      set rowcount 0

      方法二

      有两个意义上的重复记录，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

      复制代码 代码如下:

      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

      复制代码 代码如下:

      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

      复制代码 代码如下:

      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)

      最后一个select即得到了Name，Address不重复的结果集（但多了一个autoID字段，实际写时可以写

      在select子句中省去此列）

      (四)查询重复

      复制代码 代码如下:

      select * from tablename where id in (
      select id from tablename 
      group by id 
      having count(id) > 1
      )