Sql server 删除重複記錄的SQL語句

有兩個意義上的重複記錄，一是完全重複的記錄，也即所有字段均重複的記錄，二是部分關鍵字段重複的記錄，比如Name字段重複，而其他字段不一定重複或都重複可以忽略。

1、對于第一種重複，比較容易解決，使用

select distinct * from tableName

就可以得到無重複記錄的結果集。

如果該表需要删除重複的記錄（重複記錄保留1條），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

發生這種重複的原因是表設計不周産生的，增加唯一索引列即可解決。 2、這類重複問題通常要求保留重複記錄中的第一條記錄，操作方法如下

假設有重複的字段為Name,Address，要求得到這兩個字段唯一的結果集

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)

最後一個select即得到了Name，Address不重複的結果集（但多了一個autoID字段，實際寫時可以寫在select子句中省去此列） 3、部分關鍵字段重複，且記錄中有ID. 第一種方法可一次删除所有重複的..(隻保留重複中ID最小的記錄)。

delete from table where id not in ( select min(id) from table group by name) 第二種方法每次隻删除重複中ID最大的一條記錄。

delete from table where id in ( select max(id) from table group by name having count(*)>1) 4、SQL程式删除 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

自己還得出的辦法：

select   *   from   user1     where   [id]   not   in   (select   top   1   [id]   from   user1   a   where   name=user1.name)  

  --删就這樣寫  

  delete   from   user1     where   [id]   not   in   (select   top   1   [id]   from   user1   a   where   name=user1.name)

或 delete from user where id not in ( select max(id) from user where name=user.name)

delete [user] where id not in (select max(id) from [user] group by name having count(*) > 1)

max 或 min看具體情況而論。

其他方法：

----A:保留id最大的行,删除其它行  

  --方法1  

  delete   [user]   from   [user]   t    

  inner   join(select   name,max(id)   as   id   from   [user]   group   by   name)   a  

  on   t.name   =   a.name   and   t.id   <>   a.id  

  --方法2  

  delete   [user]   from   [user]   t  

  where     exists(select   *   from   [user]   where   name   =   t.name   and   id   >   t.id)  

  ----B:保留id最小的行,删除其它行  

  --方法1  

  delete   [user]   from   [user]   t    

  inner   join(select   name,min(id)   as   id   from   [user]   group   by   name)   a  

  on   t.name   =   a.name   and   t.id   <>   a.id  

  --方法2  

  delete   [user]   from   [user]   t  

  where     exists(select   *   from   [user]   where   name   =   t.name   and   id   <   t.id)  

  ----C:删除所有重複的name行,一行也不留  

  delete   [user]   from   [user]   t    

  inner   join    

  (select   id   from   [user]   a   where   exists(select   *   from   [user]   where   name   =   a.name   group   by   name   having   count(*)   >   1))   as   b  

  on   t.id   =   b.id