SQL Server2005数据库查询中使用CTE【原】

通用表表达式（CTEs）是SQL Server 2005的一项新功能。它们类似于alias（如在SELECT T1.* FROM MyTable T1中），不过功能更为强大。本质上，CTE是一个临时结果集，它仅仅存在于它发生的语句中。您可以在SELECT、INSERT、DELETE、UPDATE或CTEATE VIEW语句中建立一个CTE。CTE类似于派生表，但拥有几项优点。
CTE的优点

    与派生表不同，CTE能够引用自己本身。如果您不必存储视图，您可以用一个CTE来代替它。在一个语句中，您还可以多次引用CTE。应用CTE，您可以通过一个派生栏对结果进行分组。

    之前，我曾写过有关原子和分子查询的文章。原子查询建立一个表，而分子查询建立在原子查询之上，提供清晰与重复利用。应用CTE也可以达到同样的目的。您可以将查询区域分割成可读的“块”，然后用这些块建立一个复杂的查询。执行递归查询是CTE最重要也是最强大的功能。

    建立CTE

    CTE通过关键字WITH建立，其模板为：

WITH CTE_name[ (column_name [,...n] ) ]
AS
( CTE_query_specification ) 

    如果在CTE定义中提到的栏名称是唯一的，那么您可以不必给它们命名。不过，您同样也可以对它们重新命名。

    下面的例子应用到SQL Server 2005中的AdventureWorks样本数据库。这个数据库被高度规格化，因此需要几个连接来集合与雇员有关的信息。视图简化了这一操作，但也收集了所有有关雇员的信息，而您可能仅仅需要其中一部分资料。

    AdventureWorks的雇员数据分布在几个表中；而且，雇员与经理被存储在同一个表中（HumanResources.Employee），而他们的姓名（及其它数据）则存储在Person.Contact表中，这使得这个问题更加复杂。

    首先，我们建立一个恢复雇员姓名的CTE。

WITH cte_Employee
AS
(
SELECT e.EmployeeID, c.FirstName, c.MiddleName, c.LastName,
e.Title AS JobTitle, c.Phone, e.ManagerID
FROM HumanResources.EmployeeAS e
INNER JOIN Person.ContactAS c ON c.ContactID = e.ContactID
) 

    然后，我们可从CTE中选择一栏或几栏，就像它是一个标准的表或视图。

    接着我们再进一步。我们需要雇员和他们经理的姓名，于是我们使用CTE两次，把它自身连接起来。下面是完整的查询代码：

WITH cte_Employee
AS
(
SELECT e.EmployeeID, c.FirstName, c.MiddleName, c.LastName,
e.Title AS JobTitle, c.Phone, e.ManagerID
FROM HumanResources.EmployeeAS e
INNER JOIN Person.ContactAS c ON c.ContactID = e.ContactID
)
SELECT E.FirstName + ' ' E.LastName Employee,
M.FirstName + ' ' M.LastName Manager
FROM cte_Employee AS E
LEFT OUTER JOIN cte_Employee AS M
ON E.ManagerID = M.EmployeeID

    限制：不能在一个语句中建立两个CTE。

    总结

    CTE是SQL Server 2005的一项强大而灵活的功能。它使得SQL Server的可读性更强，更易于管理，降低了查询的复杂程度。如上所述，您可以在一个SQL Server语句中多次应用CTE。

以上是网上找到的一点教程,但实际用起来还远远不止这些,下面有一个我写的例子,经过反复琢磨终于出炉了

 

CODE

/*

--董广祥 脚本日期: 06/23/2009 18:19:17 */

CREATE PROCEDURE [dbo].[masterialStat]
    @CName NVARCHAR(50),
    @modelType NVARCHAR(20),
    @StartDate SMALLDATETIME,
    @EndDate SMALLDATETIME
AS
    WITH    tb0 ( CName, beginningStock, CurrentPeriodInput, CurrentPeriodOutput, termEndStock )
              AS ( SELECT   vyg.CName,
                            SUM(amout)
                            - ISNULL(( SELECT   SUM(amount)
                                       FROM     vyGinYillOutDetail vyd --减去出库
                                       WHERE    vyd.outPutDateTime < @EndDate
                                                AND vyg.CName = vyd.CName
                                     ), 0)
                            - ISNULL(( SELECT   SUM(amount)
                                       FROM     vRackScrap vr --减去报废
                                       WHERE    outPutDateTime < @EndDate
                                                AND vyg.CName = vr.CName
                                     ), 0),
                            0,
                            0,
                            0
                   FROM     vyGinYillDetail vyg
                   WHERE    vyg.CName LIKE '%' + @CName + '%'
                            AND vyg.category LIKE '%' + @modelType + '%'
                            AND vyg.YillDate < @StartDate
                   GROUP BY vyg.CName
 --期初结存
                 ) ,
            tb2 ( CName, beginningStock, CurrentPeriodInput, CurrentPeriodOutput, termEndStock )
              AS ( SELECT   CName,
                            0,
                            0,
                            0,
                            SUM(amout)
                            - ISNULL(( SELECT   SUM(amount)
                                       FROM     vyGinYillOutDetail vyg
                                       WHERE    vyg.outPutDateTime > @EndDate
                                                AND vyg.CName = vyd.CName
                                     ), 0) --减去出库
                            - ISNULL(( SELECT   SUM(amount)
                                       FROM     vRackScrap vr
                                       WHERE    vr.outPutDateTime > @EndDate
                                                AND vr.CName = vyd.CName
                                     ), 0) --减去报废
                   FROM     vyGinYillDetail vyd
                   WHERE    vyd.CName LIKE '%' + @CName + '%'
                            AND category LIKE '%' + @modelType + '%'
                            AND YillDate > @StartDate
                   GROUP BY CName --期末结存
                 ) ,
            tb3 ( CName, beginningStock, CurrentPeriodInput, CurrentPeriodOutput, termEndStock )
              AS ( SELECT   CName,
                            0,
                            SUM(amout),
                            0,
                            0
                   FROM     vyGinYillDetail
                   WHERE    CName LIKE '%' + @CName + '%'
                            AND category LIKE '%' + @modelType + '%'
                            AND YillDate >= @StartDate
                            AND YillDate <= @EndDate
                   GROUP BY CName --本期入库
                 ) ,
            tb4 ( CName, beginningStock, CurrentPeriodInput, CurrentPeriodOutput, termEndStock )
              AS ( SELECT   CName,
                            0,
                            0,
                            SUM(amount),
                            0
                   FROM     vyGinYillOutDetail
                   WHERE    CName LIKE '%' + @CName + '%'
                            AND category LIKE '%' + @modelType + '%'
                            AND outPutDateTime >= @StartDate
                            AND outPutDateTime <= @EndDate
                   GROUP BY CName --本期出库
                 ) ,
            tb5 ( CName, beginningStock, CurrentPeriodInput, CurrentPeriodOutput, termEndStock )
              AS ( SELECT   ISNULL(tb0.CName, tb3.CName),
                            ISNULL(tb0.beginningStock, 0),
                            ISNULL(tb3.CurrentPeriodInput, 0),
                            0,
                            0
                   FROM     tb0
                            FULL JOIN tb3 ON tb0.CName = tb3.CName --填充期初结存,本期入库
                 ) ,
            tb6 ( CName, beginningStock, CurrentPeriodInput, CurrentPeriodOutput, termEndStock )
              AS ( SELECT   ISNULL(tb5.CName, tb4.CName),
                            ISNULL(tb5.beginningStock, 0),
                            ISNULL(tb5.CurrentPeriodInput, 0),
                            ISNULL(tb4.CurrentPeriodOutput, 0),
                            0
                   FROM     tb5
                            FULL JOIN tb4 ON tb5.CName = tb4.CName
 --填充期初结存,本期入库,本期出库
                 ) ,
            tb7 ( CName, beginningStock, CurrentPeriodInput, CurrentPeriodOutput, termEndStock )
              AS ( SELECT   ISNULL(tb6.CName, tb2.CName),
                            ISNULL(tb6.beginningStock, 0),
                            ISNULL(tb6.CurrentPeriodInput, 0),
                            ISNULL(tb6.CurrentPeriodOutput, 0),
                            ISNULL(tb2.termEndStock, 0)
                   FROM     tb6
                            FULL JOIN tb2 ON tb6.CName = tb2.CName
 --填充期初结存,本期入库,本期出库,期末结存
                 )
        SELECT  CName,
                beginningStock,
                CurrentPeriodInput,
                CurrentPeriodOutput,
                termEndStock,
                ( beginningStock + CurrentPeriodInput - CurrentPeriodOutput
                  + termEndStock ) Stock
        FROM    tb7

本例出自:http://www.cnblogs.com/myssh/archive/2009/06/24/1509896.html