假如有两个关联表，是一对多关系的主子表。如下：
主表
CREATE TABLE [dbo].[CourseT](
[CourseID] [int] IDENTITY(1,1) NOT NULL,
[CourseName] [nchar](10) COLLATE Chinese_PRC_CI_AS_WS NULL
) ON [PRIMARY]
字表
CREATE TABLE [dbo].[Broad](
[BroadID] [int] IDENTITY(1,1) NOT NULL,
[CourseID] [int] NULL,
[BroadName] [nvarchar](50) COLLATE Chinese_PRC_CI_AS_WS NULL
) ON [PRIMARY]
如果数据取自CourseT表，我们想查询Broad表中记录对应的CourseT表中的记录，且按CourseID的降序只取一次，在SQL2005中SQL如下
with temp as
(
select distinct courseid from Broad
),
temp2 as
(
select courseid , ROW_NUMBER() OVER(ORDER BY courseid desc) AS row_num
from temp
)
select CourseT.* from CourseT, temp2 where courset.courseid=temp2.courseid order by row_num
如果数据取自CourseT和Broad表，我们想查询Broad表中记录对应的CourseT表中的记录，且按CourseID的降序只取一次，我们可以如下写：
with temp as
(
select courseid, broadid, row_number() over(order by courseid desc, broadid desc ) as rownum from broad
),
temp2 as
(
select temp.courseid, temp.broadid from temp where rownum=1
union
select temp.courseid, temp.broadid from temp, temp as temp0 where temp.rownum = temp0.rownum+1 and temp.courseid <> temp0.courseid
)
select CourseT.*, broad.broadid, broad.broadname from CourseT, broad, temp2
where courset.courseid=broad.courseid and temp2.courseid = courset.courseid and temp2.broadid = broad.broadid order by
broad.courseid desc ,broad.broadid desc
经牛人宪哥帮忙，又想出一个更好的方案如下：
select CourseT.CourseID,CourseName,b.BroadID,b.BroadName
from CourseT,broad b,(select max(broadid) bid,CourseID from broad group by courseid ) t
where
CourseT.CourseID=b.CourseId and b.CourseID=t.courseid and b.broadid=t.bid
http://www.cnblogs.com/laiwen/archive/2006/12/30/607690.html
