品味SQL Server 2005的幾個新功能
SQL Server 2005相對于SQL Server 2000改進(jìn)很大,有些還是非常實(shí)用的。舉幾個例子來簡單說明 這些例子我引用了Northwind庫。
1. TOP 表達(dá)式
SQL Server 2000的TOP是個固定值,是不是覺得不爽,現(xiàn)在改進(jìn)了。
--前n名的訂單
declare @n int set @n = 10 select TOP(@n) * from Orders;
2. 分頁
不知各位過去用SQL Server 2000是怎么分頁的,大多都用到了臨時表。SQL Server 2005一句話就支持分頁,性能據(jù)說也非常不錯。
--按Freight從小到大排序,求20到30行的結(jié)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沒有異常,T-SQL必須逐行檢查錯誤代碼,對于習(xí)慣了try catch程序員,2005是不是更加親切:
SET XACT_ABORT ON -- 打開 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. 通用表達(dá)式CTE
通過表達(dá)式可免除你過去創(chuàng)建臨時表的麻煩。
--例子:結(jié)合通用表達(dá)式進(jìn)行分頁
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;
特別,通過表達(dá)式還支持遞歸。
6. 直接發(fā)布Web Service
想要把store procedure變成Web Service就用這個吧,.NET, IIS都不需要,通過Windows 2003的HTTP Protocol Stack直接發(fā)布WebService,用這個功能需要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就發(fā)布好了,敲入http://localhost/sql/orders?wsdl得到wsdl;
