查询表中重复字段的记录和删除表中重复字段记录的sql语句

方法一

    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

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）

examp：

insert into table4 values ('025','南京')
insert into table4 values ('025','南京')
insert into table4 values ('025','南京')
insert into table4 values ('021','上海') 
insert into table4 values ('021','上海')
insert into table4 values ('021','上海')
insert into table4 values ('020','广州') 
insert into table4 values ('020','广州')

实现删除：

declare @a1 varchar(20),@a2 varchar(20),@z int
declare LS cursor for select code,name,count(*) from table4
group by code,name
having count(*)>1
open LS
fetch LS into @a1,@a2,@z
while @@fetch_status=0
   begin
      set @z=@z-1
      set rowcount @z      ----实现删除的行数
      delete from table4 where code=@a1 and name=@a2
      fetch LS into @a1,@a2,@z
   end

close LS
deallocate LS

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

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、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)