此文向大家介绍的是SQL Server查找与删除重复记录的实际操作方法，数据库重复记录中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。

　　即要知道哪些记录是重复 的,怎么弄?

　　方法一：

　　执行：

　　select dd,count(*) from table group by dd having count(*)>1 如何用sql 查找两个字段重复的记录，并列出重复记录

　　表名为CJB, 列出其中XH和KCMC字段都重复的记录

　　执行：

　　select * from CJB a join (  select XH,KCMC from CJB group by XH,KCMC  having count(*)>1) b on a.XH=b.XH and a.KCMC=b.KCMC order by   a.KCMC ,a.XH 实例：

　　select productID,searchkay from shortkay group by searchkay,productID having count(*) > 1 order by searchkay  等同于下面这句：

　　select a.ID,a.productID,a.searchkay from shortkay a join (select productID,searchkay from shortkay group by productID,  searchkay having count(*)>1) b on a.productID=b.productID and a.searchkay=b.searchkay order by a.searchkay, a.productID  1、SQL Server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

　　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

　　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）

　　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

　　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、SQL Server查找表中多余的重复记录（多个字段），不包含rowid最小的记录

　　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)

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