if not object_id('cj')is null
drop table cj
go
create table cj(stuName nvarchar(10),KCM nvarchar(10),cj numeric(5,2))
insert into cj select '张三','语文',98
union select '李四','语文',89
union select '王五','语文',67
union select '周攻','语文',56
union select '张三','数学',89
union select '李四','数学',78
union select '王五','数学',90
union select '周攻','数学',87
方法一:
select stuname from
(select stuName,kcm,(select count(*) from cj where stuname!=a.stuname and kcm=a.kcm and cj>a.cj) cnt from cj a) x
group by stuname having max(cnt)<=1
go
方法二:
SELECT stuname FROM cj1 a
where cj IN(SELECT TOP 2 cj FROM cj1 WHERE kcm=a.kcm ORDER BY cj desc)
GROUP BY stuname HAVING(count(1)>1)
方法三:
select distinct stuname from cj a
where not exists(select kcm from cj b where a.stuname=stuname
and (select count(*) from cj where kcm=b.kcm and stuname!=a.stuname and cj>b.cj)>1)
我想问一下这三条语句的意思,因为我修改表的数据测试的结果貌似不一样,谢谢
drop table cj
go
create table cj(stuName nvarchar(10),KCM nvarchar(10),cj numeric(5,2))
insert into cj select '张三','语文',98
union select '李四','语文',89
union select '王五','语文',67
union select '周攻','语文',56
union select '张三','数学',89
union select '李四','数学',78
union select '王五','数学',90
union select '周攻','数学',87
方法一:
select stuname from
(select stuName,kcm,(select count(*) from cj where stuname!=a.stuname and kcm=a.kcm and cj>a.cj) cnt from cj a) x
group by stuname having max(cnt)<=1
go
方法二:
SELECT stuname FROM cj1 a
where cj IN(SELECT TOP 2 cj FROM cj1 WHERE kcm=a.kcm ORDER BY cj desc)
GROUP BY stuname HAVING(count(1)>1)
方法三:
select distinct stuname from cj a
where not exists(select kcm from cj b where a.stuname=stuname
and (select count(*) from cj where kcm=b.kcm and stuname!=a.stuname and cj>b.cj)>1)
我想问一下这三条语句的意思,因为我修改表的数据测试的结果貌似不一样,谢谢
(select stuName,kcm,(select count(*) from cj where stuname!=a.stuname and kcm=a.kcm and cj>a.cj) cnt from cj a) x
group by stuname having max(cnt) <=1 这个是加排序列
查每个分類前N条记录
-- 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)
*/
insert into cj select '张三','语文',12
union select '李四','语文',89
union select '王五','语文',67
union select '周攻','语文',56
union select '张三','数学',89
union select '李四','数学',78 union select '周攻','数学',87 这样三条语句不等效
if not object_id('cj')is null
drop table cj
go
create table cj(stuName nvarchar(10),KCM nvarchar(10),cj numeric(5,2))
insert into cj select '张三','语文',98
union select '李四','语文',89
union select '王五','语文',67
union select '周攻','语文',56
union select '张三','数学',89
union select '李四','数学',78
union select '王五','数学',90
union select '周攻','数学',87 select * from
(select *, cnt=(select count(1) from cj where stuName != A.stuName and
kcm = A.kcm and cj > A.cj )from cj A
)B
where B.cnt <2 order by KCM ,cj desc==========
---每科前两名的
stuName KCM cj cnt
---------- ---------- --------------------------------------- -----------
王五 数学 90.00 0
张三 数学 89.00 1
张三 语文 98.00 0
李四 语文 89.00 1(4 行受影响)