delete t from tb t where exists(select 1 from  tb where DocumentID=DocumentID and DocumentName=t.DocumentName and id<t.id)

------解决方案--------------------
SQL code
delete from  document where not exsits (select max(id),DocumentID,DocumentName
from document )

------解决方案--------------------
SQL code

with cte as
(select *,row_number()over(partition by DocumentID,DocumentName order by getdate())as RN from tb)
delete from cte where RN>1

------解决方案--------------------

SQL code
----------------------------
-- Author  :fredrickhu(小F，向高手学习)
-- Date    :2011-11-03 16:15:46
-- Version:
--      Microsoft SQL Server 2008 R2 (RTM) - 10.50.1617.0 (Intel X86) 
--    Apr 22 2011 11:57:00 
--    Copyright (c) Microsoft Corporation
--    Enterprise Evaluation Edition on Windows NT 6.1 <X64> (Build 7600: ) (WOW64)
--
----------------------------
--> 测试数据：[tb]
if object_id('[tb]') is not null drop table [tb]
go 
create table [tb]([ID] uniqueidentifier,[DocumentID] int,[DocumentName] varchar(4))
insert [tb]
select '8941ada0-bc47-4ee3-9bae-5dd660bc75e5',1,'doc1' union all
select 'bc53ec55-f776-4f88-91e5-827e1d9595a8',1,'doc1' union all
select '547d2b1a-3233-41dd-8578-d3a25f3ef911',1,'doc1'
--------------开始查询--------------------------
delete t from tb t where exists(select 1 from  tb where DocumentID=DocumentID and DocumentName=t.DocumentName and id<t.id)

select * from tb 
----------------结果----------------------------
/* ID                                   DocumentID  DocumentName
------------------------------------ ----------- ------------
8941ADA0-BC47-4EE3-9BAE-5DD660BC75E5 1           doc1

(1 行受影响)
*/

------解决方案--------------------
SQL code
create table document(ID varchar(50),DocumentID int,DocumentName varchar(10))
insert into document select '8941ada0-bc47-4ee3-9bae-5dd660bc75e5',1,'doc1'
insert into document select 'bc53ec55-f776-4f88-91e5-827e1d9595a8',1,'doc1'
insert into document select '547d2b1a-3233-41dd-8578-d3a25f3ef911',1,'doc1'
go
delete t from document t 
where exists(select 1 from document where DocumentID=t.DocumentID and DocumentName=t.DocumentName and ID>t.id)
select * from document 
/*
ID                                                 DocumentID  DocumentName
-------------------------------------------------- ----------- ------------
bc53ec55-f776-4f88-91e5-827e1d9595a8               1           doc1

(1 行受影响)
*/
go
drop table document

------解决方案--------------------
SQL code
delete from  document where not exsits (select max(id),DocumentID,DocumentName
from document  where  DocumentID=DocumentID and DocumentName=DocumentName )