天枫庄资源网 Design By www.wosibo.com
复制代码 代码如下:
/****** 创建表 ******/
if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[Table]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [dbo].[Table]
GO
Create TABLE [dbo].[Table] (
[ID] [int] IDENTITY (1, 1) NOT NULL ,
[Y] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[X] [smalldatetime] NOT NULL
) ON [PRIMARY]
GO
--插入数据
Insert INTO [Table](Y, X) values('CCC', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('AAA', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('AAA', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('BBB', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('BBB', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('BBB', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('CCC', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('AAA', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('CCC', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('DDD', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('DDD', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('DDD', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('EEE', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('EEE', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('EEE', '2007-03-03 03:03:03')
GO
/****** 创建表 ******/
if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[Table]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [dbo].[Table]
GO
Create TABLE [dbo].[Table] (
[ID] [int] IDENTITY (1, 1) NOT NULL ,
[Y] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[X] [smalldatetime] NOT NULL
) ON [PRIMARY]
GO
--插入数据
Insert INTO [Table](Y, X) values('CCC', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('AAA', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('AAA', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('BBB', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('BBB', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('BBB', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('CCC', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('AAA', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('CCC', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('DDD', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('DDD', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('DDD', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('EEE', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('EEE', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('EEE', '2007-03-03 03:03:03')
GO解决“每个Y的最新X”经典SQL问题:以下几种方法真是八仙过海
复制代码 代码如下:
Select ID, Y, X
FROM [Table] T1
Where (NOT EXISTS
(Select 1
FROM [Table] T2
Where (T2.Y = T1 .Y) AND (T2.X > T1 .X or
T2.X = T1 .X AND T2.ID > T1 .ID)))
/*****************************************************************************/
Select *
FROM [Table]
Where ID IN
(Select MAX(T1.ID)
FROM [Table] T1 JOIN
(Select y, MAX(x) x
FROM [Table]
GROUP BY y) T2 ON T1.Y = T2.Y AND T1.x = T2.x
GROUP BY T1.y)
/*****************************************************************************/
Select T .ID, T .Y, T .X
FROM [Table] T INNER JOIN
(Select MAX(T1.ID) AS ID
FROM [Table] T1 JOIN
(Select y, MAX(x) x
FROM [Table]
GROUP BY y) T2 ON T1.Y = T2.Y AND T1.x = T2.x
GROUP BY T1.y) T2 ON T .ID = T2.ID
/*****************************************************************************/
Select *
FROM [Table] T1
Where ID IN
(Select TOP 1 ID
FROM [Table]
Where Y = T1.Y
orDER BY X DESC)
/*****************************************************************************/
Select *
FROM [Table] T1
Where (ID =
(Select TOP 1 ID
FROM [Table]
Where Y = T1.Y
orDER BY X DESC, ID DESC))
/*****************************************************************************/
/*****************************************************************************/
Select ID, Y, X
FROM [Table] T1
Where (NOT EXISTS
(Select 1
FROM [Table] T2
Where (T2.Y = T1 .Y) AND (T2.X > T1 .X or
T2.X = T1 .X AND T2.ID > T1 .ID)))
/*****************************************************************************/
Select *
FROM [Table]
Where ID IN
(Select MAX(T1.ID)
FROM [Table] T1 JOIN
(Select y, MAX(x) x
FROM [Table]
GROUP BY y) T2 ON T1.Y = T2.Y AND T1.x = T2.x
GROUP BY T1.y)
/*****************************************************************************/
Select T .ID, T .Y, T .X
FROM [Table] T INNER JOIN
(Select MAX(T1.ID) AS ID
FROM [Table] T1 JOIN
(Select y, MAX(x) x
FROM [Table]
GROUP BY y) T2 ON T1.Y = T2.Y AND T1.x = T2.x
GROUP BY T1.y) T2 ON T .ID = T2.ID
/*****************************************************************************/
Select *
FROM [Table] T1
Where ID IN
(Select TOP 1 ID
FROM [Table]
Where Y = T1.Y
orDER BY X DESC)
/*****************************************************************************/
Select *
FROM [Table] T1
Where (ID =
(Select TOP 1 ID
FROM [Table]
Where Y = T1.Y
orDER BY X DESC, ID DESC))
/*****************************************************************************
/效率嘛,在不同的字段建立索引速度都不尽相同,使用者见仁见智了.
第一种方法速度在各方面都不错,而且在Y列在建立索引,可以大大优化查询速度。
/****** 创建表 ******/
if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[Table]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [dbo].[Table]
GO
Create TABLE [dbo].[Table] (
[ID] [int] IDENTITY (1, 1) NOT NULL ,
[Y] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[X] [smalldatetime] NOT NULL
) ON [PRIMARY]
GO
--插入数据
Insert INTO [Table](Y, X) values('CCC', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('AAA', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('AAA', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('BBB', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('BBB', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('BBB', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('CCC', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('AAA', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('CCC', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('DDD', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('DDD', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('DDD', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('EEE', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('EEE', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('EEE', '2007-03-03 03:03:03')
GO
/****** 创建表 ******/
if exists (select * from dbo.sysobjects where id = object_id(N'[dbo].[Table]') and OBJECTPROPERTY(id, N'IsUserTable') = 1)
drop table [dbo].[Table]
GO
Create TABLE [dbo].[Table] (
[ID] [int] IDENTITY (1, 1) NOT NULL ,
[Y] [nvarchar] (50) COLLATE Chinese_PRC_CI_AS NOT NULL ,
[X] [smalldatetime] NOT NULL
) ON [PRIMARY]
GO
--插入数据
Insert INTO [Table](Y, X) values('CCC', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('AAA', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('AAA', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('BBB', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('BBB', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('BBB', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('CCC', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('AAA', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('CCC', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('DDD', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('DDD', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('DDD', '2007-03-03 03:03:03')
Insert INTO [Table](Y, X) values('EEE', '2007-01-01 01:01:01')
Insert INTO [Table](Y, X) values('EEE', '2007-02-02 02:02:02')
Insert INTO [Table](Y, X) values('EEE', '2007-03-03 03:03:03')
GO解决“每个Y的最新X”经典SQL问题:以下几种方法真是八仙过海
复制代码 代码如下:
Select ID, Y, X
FROM [Table] T1
Where (NOT EXISTS
(Select 1
FROM [Table] T2
Where (T2.Y = T1 .Y) AND (T2.X > T1 .X or
T2.X = T1 .X AND T2.ID > T1 .ID)))
/*****************************************************************************/
Select *
FROM [Table]
Where ID IN
(Select MAX(T1.ID)
FROM [Table] T1 JOIN
(Select y, MAX(x) x
FROM [Table]
GROUP BY y) T2 ON T1.Y = T2.Y AND T1.x = T2.x
GROUP BY T1.y)
/*****************************************************************************/
Select T .ID, T .Y, T .X
FROM [Table] T INNER JOIN
(Select MAX(T1.ID) AS ID
FROM [Table] T1 JOIN
(Select y, MAX(x) x
FROM [Table]
GROUP BY y) T2 ON T1.Y = T2.Y AND T1.x = T2.x
GROUP BY T1.y) T2 ON T .ID = T2.ID
/*****************************************************************************/
Select *
FROM [Table] T1
Where ID IN
(Select TOP 1 ID
FROM [Table]
Where Y = T1.Y
orDER BY X DESC)
/*****************************************************************************/
Select *
FROM [Table] T1
Where (ID =
(Select TOP 1 ID
FROM [Table]
Where Y = T1.Y
orDER BY X DESC, ID DESC))
/*****************************************************************************/
/*****************************************************************************/
Select ID, Y, X
FROM [Table] T1
Where (NOT EXISTS
(Select 1
FROM [Table] T2
Where (T2.Y = T1 .Y) AND (T2.X > T1 .X or
T2.X = T1 .X AND T2.ID > T1 .ID)))
/*****************************************************************************/
Select *
FROM [Table]
Where ID IN
(Select MAX(T1.ID)
FROM [Table] T1 JOIN
(Select y, MAX(x) x
FROM [Table]
GROUP BY y) T2 ON T1.Y = T2.Y AND T1.x = T2.x
GROUP BY T1.y)
/*****************************************************************************/
Select T .ID, T .Y, T .X
FROM [Table] T INNER JOIN
(Select MAX(T1.ID) AS ID
FROM [Table] T1 JOIN
(Select y, MAX(x) x
FROM [Table]
GROUP BY y) T2 ON T1.Y = T2.Y AND T1.x = T2.x
GROUP BY T1.y) T2 ON T .ID = T2.ID
/*****************************************************************************/
Select *
FROM [Table] T1
Where ID IN
(Select TOP 1 ID
FROM [Table]
Where Y = T1.Y
orDER BY X DESC)
/*****************************************************************************/
Select *
FROM [Table] T1
Where (ID =
(Select TOP 1 ID
FROM [Table]
Where Y = T1.Y
orDER BY X DESC, ID DESC))
/*****************************************************************************
/效率嘛,在不同的字段建立索引速度都不尽相同,使用者见仁见智了.
第一种方法速度在各方面都不错,而且在Y列在建立索引,可以大大优化查询速度。
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每个Y的最新X,经典sql语句
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天枫庄资源网 Design By www.wosibo.com
暂无一条语句简单解决“每个Y的最新X”的经典sql语句的评论...
稳了!魔兽国服回归的3条重磅消息!官宣时间再确认!
昨天有一位朋友在大神群里分享,自己亚服账号被封号之后居然弹出了国服的封号信息对话框。
这里面让他访问的是一个国服的战网网址,com.cn和后面的zh都非常明白地表明这就是国服战网。
而他在复制这个网址并且进行登录之后,确实是网易的网址,也就是我们熟悉的停服之后国服发布的暴雪游戏产品运营到期开放退款的说明。这是一件比较奇怪的事情,因为以前都没有出现这样的情况,现在突然提示跳转到国服战网的网址,是不是说明了简体中文客户端已经开始进行更新了呢?
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