利用sql2005的新特性实现根据子表条件得到的主表键且按其排序取出对应主子表记录的方法

王朝mssql·作者佚名  2008-05-31
窄屏简体版  字體: |||超大  

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

 
 
 
免责声明:本文为网络用户发布,其观点仅代表作者个人观点,与本站无关,本站仅提供信息存储服务。文中陈述内容未经本站证实,其真实性、完整性、及时性本站不作任何保证或承诺,请读者仅作参考,并请自行核实相关内容。
 
 
© 2005- 王朝網路 版權所有 導航