品味SQL Server 2005的几个新功能
SQL Server 2005相对于SQL Server 2000改进很大,有些还是非常实用的。举几个例子来简单说明 这些例子我引用了Northwind库。
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。
--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;