----------------------------
-- Author  :TravyLee(物是人非事事休，欲语泪先流！)
-- Date    :2012-09-12 14:33:38
-- Version:
--      Microsoft SQL Server 2005 - 9.00.1399.06 (Intel X86) 
--    Oct 14 2005 00:33:37 
--    Copyright (c) 1988-2005 Microsoft Corporation
--    Developer Edition on Windows NT 6.1 (Build 7601: Service Pack 1)
--
----------------------------
--> 测试数据：[test]
if object_id('[test]') is not null drop table [test]
go 
create table [test]([单位] varchar(6),[发货单号] int,[销售数量] numeric(14,10),[已出库数量] numeric(14,10))
insert [test]
select '箱(12)',120800815,3000.0000000000,3000.0000000000 union all
select '箱(12)',120800672,2500.0000000000,596.0000000000 union all
select '箱(12)',120800672,2500.0000000000,1800.0000000000 union all
select '箱(12)',120800672,2500.0000000000,104.0000000000 union all
select '箱(24)',120800870,400.0000000000,400.0000000000
go

select 
    distinct [发货单号],
    sum([销售数量])over(partition by getdate()) as [销售数量],
    sum([已出库数量])over(partition by [发货单号]) as [已出库数量]
from
    test

/*
[发货单号] [销售数量] [已出库数量]
--------------------------
120800672    10900.0000000000    2500.0000000000
120800815    10900.0000000000    3000.0000000000
120800870    10900.0000000000    400.0000000000
*/

不晓得你具体要什么结果