一张产品表,ID(主键),NAME
一张图片表,ID,ProUrl(图片路径),ProID(外键,产品表)现在是:有些产品不只是一张图片;我想实现 的就是不论有几张图片的,都只显示一张出来
当然如果只有一张图片的产品也要显示出来哦!!!
一张图片表,ID,ProUrl(图片路径),ProID(外键,产品表)现在是:有些产品不只是一张图片;我想实现 的就是不论有几张图片的,都只显示一张出来
当然如果只有一张图片的产品也要显示出来哦!!!
-- Author: liangCK 小梁
-- Title : 查每个分组前N条记录
-- Date : 2008-11-13 17:19:23
-----------------------------------> 生成测试数据: #T
IF OBJECT_ID('tempdb.dbo.#T') IS NOT NULL DROP TABLE #T
CREATE TABLE #T (ID VARCHAR(3),GID INT,Author VARCHAR(29),Title VARCHAR(39),Date DATETIME)
INSERT INTO #T
SELECT '001',1,'邹建','深入浅出SQLServer2005开发管理与应用实例','2008-05-10' UNION ALL
SELECT '002',1,'胡百敬','SQLServer2005性能调校','2008-03-22' UNION ALL
SELECT '003',1,'格罗夫Groff.J.R.','SQL完全手册','2009-07-01' UNION ALL
SELECT '004',1,'KalenDelaney','SQLServer2005技术内幕存储引擎','2008-08-01' UNION ALL
SELECT '005',2,'Alex.Kriegel.Boris.M.Trukhnov','SQL宝典','2007-10-05' UNION ALL
SELECT '006',2,'飞思科技产品研发中心','SQLServer2000高级管理与开发','2007-09-10' UNION ALL
SELECT '007',2,'胡百敬','SQLServer2005数据库开发详解','2008-06-15' UNION ALL
SELECT '008',3,'陈浩奎','SQLServer2000存储过程与XML编程','2005-09-01' UNION ALL
SELECT '009',3,'赵松涛','SQLServer2005系统管理实录','2008-10-01' UNION ALL
SELECT '010',3,'黄占涛','SQL技术手册','2006-01-01'--SQL查询如下:--按GID分组,查每个分组中Date最新的前2条记录
--1.字段ID唯一时:
SELECT * FROM #T AS T WHERE ID IN(SELECT TOP 2 ID FROM #T WHERE GID=T.GID ORDER BY Date DESC)--2.如果ID不唯一时:
SELECT * FROM #T AS T WHERE 2>(SELECT COUNT(*) FROM #T WHERE GID=T.GID AND Date>T.Date)--SQL Server 2005 使用新方法--3.使用ROW_NUMBER()进行排位分组
SELECT ID,GID,Author,Title,Date
FROM
(
SELECT rid=ROW_NUMBER() OVER(PARTITION BY GID ORDER BY Date DESC),*
FROM #T
) AS T
WHERE rid<=2--4.使用APPLY
SELECT DISTINCT b.*
FROM #T AS a
CROSS APPLY
(
SELECT TOP(2) * FROM #T WHERE a.GID=GID ORDER BY Date DESC
) AS b
--结果
/*ID GID Author Title Date
---- ----------- ----------------------------- --------------------------------------- -----------------------
003 1 格罗夫Groff.J.R. SQL完全手册 2009-07-01 00:00:00.000
004 1 KalenDelaney SQLServer2005技术内幕存储引擎 2008-08-01 00:00:00.000
005 2 Alex.Kriegel.Boris.M.Trukhnov SQL宝典 2007-10-05 00:00:00.000
007 2 胡百敬 SQLServer2005数据库开发详解 2008-06-15 00:00:00.000
009 3 赵松涛 SQLServer2005系统管理实录 2008-10-01 00:00:00.000
010 3 黄占涛 SQL技术手册 2006-01-01 00:00:00.000(6 行受影响)
*/
*
from
产品表 a,图片表 b
where
a.id=b.ProID
and
ID=(select min(id) from 图片表 where ProID=b.ProID)
select m.* , n.*
from 产品表 m, 图片表 n
where m.ID = n.ProID and n.ID = (select min(id) from 图片表 where ProID = n.ProID)select m.* , n.*
from 产品表 m, 图片表 n
where m.ID = n.ProID and not exists (select 1 from 图片表 where ProID = n.ProID and id < n.id)select m.* , n.*
from 产品表 m, 图片表 n
where m.ID = n.ProID and n.ID = (select max(id) from 图片表 where ProID = n.ProID)select m.* , n.*
from 产品表 m, 图片表 n
where m.ID = n.ProID and not exists (select 1 from 图片表 where ProID = n.ProID and id > n.id)
from 产品表 m, 图片表 n
where m.ID = n.ProID and not exists (select 1 from 图片表 where ProID = n.ProID and id < n.id)