SQL Server 2005's new added Ranking functions

Ranking functions return a ranking value for each row in a partition. Depending on the function that is used, some rows might receive the same value as other rows. Ranking functions are nondeterministic.

Transact-SQL provides the following ranking functions:

RANK	NTILE
DENSE_RANK	ROW_NUMBER

Examples

The following shows the four ranking functions used in the same query. For function specific examples, see each ranking function.

USE AdventureWorks2008R2;
GO
SELECT p.FirstName, p.LastName
   ,ROW_NUMBER() OVER (ORDER BY a.PostalCode) AS 'Row Number'
   ,RANK() OVER (ORDER BY a.PostalCode) AS 'Rank'
   ,DENSE_RANK() OVER (ORDER BY a.PostalCode) AS 'Dense Rank'
   ,NTILE(4) OVER (ORDER BY a.PostalCode) AS 'Quartile'
   ,s.SalesYTD, a.PostalCode
FROM Sales.SalesPerson s
   INNER JOIN Person.Person p
       ON s.BusinessEntityID = p.BusinessEntityID
   INNER JOIN Person.Address a
       ON a.AddressID = p.BusinessEntityID
WHERE TerritoryID IS NOT NULL
   AND SalesYTD <> 0;

Here is the result set.

FirstName	LastName	Row Number	Rank	Dense Rank	Quartile	SalesYTD	PostalCode
Michael	Blythe	1	1	1	1	4557045.0459	98027
Linda	Mitchell	2	1	1	1	5200475.2313	98027
Jillian	Carson	3	1	1	1	3857163.6332	98027
Garrett	Vargas	4	1	1	1	1764938.9859	98027
Tsvi	Reiter	5	1	1	2	2811012.7151	98027
Shu	Ito	6	6	2	2	3018725.4858	98055
José	Saraiva	7	6	2	2	3189356.2465	98055
David	Campbell	8	6	2	3	3587378.4257	98055
Tete	Mensa-Annan	9	6	2	3	1931620.1835	98055
Lynn	Tsoflias	10	6	2	3	1758385.926	98055
Rachel	Valdez	11	6	2	4	2241204.0424	98055
Jae	Pak	12	6	2	4	5015682.3752	98055
Ranjit	Varkey Chudukatil	13	6	2	4	3827950.238	98055

select Nth to Mth record from a table

select top 10 * from (select top 40 * from tb desc) asc select top 40 * from A where id not in(select top 30 id from A) which of above 2 is more efficient? why? in sql 2005+ ,you should use SELECT col1, col2 FROM ( SELECT col1, col2, ROW_NUMBER() OVER (ORDER BY ID) AS RowNum FROM MyTable ) AS MyDerivedTable WHERE MyDerivedTable.RowNum BETWEEN @startRow AND @endRow

Relationships Between Classes

Relationships Between Classes

In a class diagram, obviously you can't have classes just floating around; you need to see the relationship between them. The following table shows the kinds of relationships between classes, their notation, and what they mean.

Sr. No.	Relation	Symbol	Description
1	Association		When two classes are connected to each other in any way, an association relation is established. For example: A "student studies in a college" association can be shown as:
1 a.	Multiplicity		An example of this kind of association is many students belonging to the same college. Hence, the relation shows a star sign near the student class (one to many, many to many, and so forth kind of relations).
1 b.	Directed Association		Association between classes is bi-directional by default. You can define the flow of the association by using a directed association. The arrowhead identifies the container-contained relationship.
1 c.	Reflexive Association	No separate symbol. However, the relation will point back at the same class.	An example of this kind of relation is when a class has a variety of responsibilities. For example, an employee of a college can be a professor, a housekeeper, or an administrative assistant.
2	Aggregation		When a class is formed as a collection of other classes, it is called an aggregation relationship between these classes. It is also called a "has a" relationship.
2 a.	Composition		Composition is a variation of the aggregation relationship. Composition connotes that a strong life cycle is associated between the classes.
3	Inheritance/Generalization		Also called an "is a" relationship, because the child class is a type of the parent class. Generalization is the basic type of relationship used to define reusable elements in the class diagram. Literally, the child classes "inherit" the common functionality defined in the parent class.
4	Realization		In a realization relationship, one entity (normally an interface) defines a set of functionalities as a contract and the other entity (normally a class) "realizes" the contract by implementing the functionality defined in the contract.

ASP.NET缓存

生成高性能、可缩放的 Web 应用程序最重要的因素之一是能够在首次请求项时将这些项存储在内存中，不管它们是数据对象、页还是页的某些部分。 可以将这些项缓存或存储在 Web 服务器上或请求流中的其他软件上，如代理服务器或浏览器。 使您能够避免重新创建满足先前请求的信息，尤其是那些需要大量处理器时间或资源的信息。 ASP.NET 缓存允许您使用多种技术跨 HTTP 请求存储页输出或应用程序数据并对其进行重复使用。

ASP.NET 提供了两种您可以用来创建高性能 Web 应用程序的缓存类型。 第一种类型是输出缓存，它允许将动态页和用户控件响应存储在输出流（从发起服务器到请求浏览器）中任何具备 HTTP 1.1 缓存功能的设备上。 当后面的请求发生时，不执行页或用户控件代码，缓存的输出用于满足该请求。 第二种类型的缓存是应用程序数据缓存，可以使用它以编程方式将任意对象（如应用程序数据）存储到服务器内存中，这样您的应用程序可以节省重新创建这些对象所需的时间和资源。

输出缓存：

以声明方式设置页的可缓存性

在页中包含 @ OutputCache 指令，并定义 Duration 和 VaryByParam 特性。

在 @ OutputCache 指令中包含 Location 特性，并将其值定义为 OutputCacheLocation 枚举中的下列值之一：Any、Client、Downstream、Server、ServerAndClient 或 None。

下面的代码演示如何将页的可缓存性设置为 60 秒：

<%@ OutputCache Duration="60" VaryByParam="None"%>

保存页面的多个版本：

<%@ OutputCache Duration="60" VaryByParam="productId"%>

这样，形如

www.goodasp.net?productId=15

www.goodasp.net?productId=1357

的页面各自有一个缓存版本

或许我们在页面里一个dropdownlist ddlCustomer,一个grid gridBuyDetail，grid根据所选的dropdownlist的值

呈现详细信息，我们可以设置页面缓存为：

<%@ OutputCache Duration="60" VaryByControl="productId"%>

使用缓存配置文件以声明方式设置页的可缓存性

在应用程序的 Web.config 文件中定义缓存配置文件，在配置文件中包括 duration 和 varyByParam 设置。

下面的 配置元素定义名为 Cache30Seconds 的缓存配置文件，它将在服务器上将页缓存 30 秒之久。

<caching>

  <outputCacheSettings>

    <outputCacheProfiles>

      <add name="Cache30Seconds" duration="30"

        varyByParam="none" />

    </outputCacheProfiles>

  </outputCacheSettings>

</caching>

在使用配置文件的每个 ASP.NET 页中包含 @ OutputCache 指令，并将 CacheProfile 特性设置为 Web.config 文件中定义的缓存配置文件的名称。

下面的代码指定页应当使用名为 Cache30Seconds 的缓存配置文件：

<%@ OutputCache CacheProfile="Cache30Seconds" %>

出于以下原因之一，ASP.NET 可以从缓存中移除数据：

由于服务器上的内存不足，开始一个称为“清理”的过程。
由于缓存中的项已过期。
由于项的依赖项发生了更改

uml 类图基础

UML basics: The class diagram