SQLserver2005-->T-sql新特性用法(转)

1. TOP 表达式
SQL Server 2000的TOP是个固定值，是不是觉得不爽，现在改进了。

--前n名的订单
declare @n int
set @n = 10
select TOP(@n) * from Orders

2. 分页
不知各位过去用SQL Server 2000是怎么分页的，大多都用到了临时表。SQL Server 2005一句话就支持分页，性能据说也非常不错。

 ROW_NUMBER()为每条分组记录返回一个行号，常用ROW_NUMBER() OVER(group by 分组字段 order by 排序字段)

--按Freight从小到大排序，求20到30行的结果
select * from(
    select OrderId, Freight, ROW_NUMBER() OVER(order by Freight) as row from Orders
) a
where row between 20 and 30

3. 排名

select * from(
    select OrderId, Freight, RANK() OVER(order by Freight) as rank from Orders
) a
where rank between 20 and 30

4. try ... catch
SQL Server 2000没有异常，T-SQL必须逐行检查错误代码，对于习惯了try catch程序员，2005是不是更加亲切：

SET XACT_ABORT ON  -- 打开 try功能
BEGIN TRY
    begin tran
        insert into Orders(CustomerId) values(-1)
    commit tran
    print 'commited'
END TRY
BEGIN CATCH
    rollback    
    print 'rolled back'
END CATCH

5. 通用表达式CTE
通过表达式可免除你过去创建临时表的麻烦。

--例子：结合通用表达式进行分页
WITH OrderFreight AS(
    select OrderId, Freight, ROW_NUMBER() OVER(order by Freight) as row from Orders
)
select OrderId, Freight from OrderFreight where row between 10 and 20

特别，通过表达式还支持递归。

6. 直接发布Web Service
想要把store procedure变成Web Service就用这个吧，.NET, IIS都不需要，通过Windows 2003的HTTP Protocol Stack直接发布WebService,用这个功能需要Windows 2003 sp1

--DataSet CustOrdersOrders(string customerID)
CREATE ENDPOINT Orders_Endpoint
state=started
as http(
     path='/sql/orders',
     AUTHENTICATION=(INTEGRATED),
     ports=(clear)
)
for soap(
     WebMethod 'CustOrdersOrders'(   
         name='Northwind.dbo.CustOrdersOrders'
     ),
    
     wsdl=default,
    database='Northwind',
     namespace='http://mysite.org/'
)

Web Service就发布好了，敲入http://localhost/sql/orders?wsdl得到wsdl

在http通讯时，例子代码使用的是Windows集成验证 。
给个客户端例子。

private void button1_Click(object sender, EventArgs e)
{
     localhost.Orders_Endpoint endp = new localhost.Orders_Endpoint();
     endp.Credentials = System.Net.CredentialCache.DefaultCredentials;
    object[] r = endp.CustOrdersOrders("VINET");

     DataSet ds = new DataSet();
    foreach(object o in r)
        if (o is DataSet) ds = (DataSet)o;

     dataGridView1.DataSource = ds.Tables[0];            
}