我可以在同一视图中使用稍后在SQL Server视图中计算的列吗？

Question

我可以在同一视图中使用稍后在SQL Server视图中计算的列吗？

比方说，我有以下看法：

Select 
    t1.StartMile, t2.EndMile, t2.EndMile- t1.StartMile as TotMile 
from 
    TableStarts as t1 
inner join 
    TableEnds as t2 on t1.Id = t2.Id 

有编辑视图做以下

Select 
    t1.StartMile, t2.EndMile, t2.EndMile - t1.StartMile as TotMile, 
    TotMile + 30 as EvenMoreMiles 

我尝试这样的方式，得到了错误：

Invalid column name 'TotMile'

请不要告诉我使用t2.EndMile - t1.StartMile + 30 as EvenMoreMiles。 TotMiles在我的实际代码中是一个很长的案例陈述。

我宁愿不必创建一个中间视图。

我使用SQL Server 2005的

以后添加

感谢所有的答案。我会全力投入。

的答案会提出下面的新问题：

鉴于有数千行和TotMiles如下所示，它给出的答案将是最有效的？或者创建中间视图最有效率？

CASE WHEN t .TaskType = 1 and t .StartTime < '1/1/2012' 
       THEN (tv.EndMile - tv.StartMile) 
    WHEN NOT (t .Location1_PKey = c.pkey OR t .Location2_PKey = c.pkey) 
       then (tv.EndMile - tv.StartMile) 
    WHEN (tv.EndMile - tv.StartMile) < 31 Then 0 
    ELSE (tv.EndMile - tv.StartMile - 30) 
END AS MilesAdjusted2012, 

Answer 1

您还可以使用CROSS APPLY从而可以更简洁，特别是如果你正在建立引用之前的部分别名链。

SELECT t1.StartMile, 
     t2.EndMile, 
     TotMile, 
     EvenMoreMiles, 
     AndYetMoreMiles 
FROM TableStarts AS t1 
     INNER JOIN TableEnds AS t2 
     ON t1.Id = t2.Id 
     CROSS APPLY (SELECT t2.EndMile - t1.StartMile) A(TotMile) 
     CROSS APPLY (SELECT TotMile + 30) A2(EvenMoreMiles) 
     CROSS APPLY (SELECT EvenMoreMiles + 100) A3(AndYetMoreMiles) 

Answer 2

你不能直接，但你可以建立子选择：

select StartMile,EndMile,TotMile,TotMile+30 as EvenMoreMiles from (
    Select t1.StartMile, t2.EndMile, t2.EndMile- t1.StartMile as TotMile 
    from 
    TableStarts as t1 
    inner join 
    TableEnds as t2 
    on t1.Id = t2.Id 
) t 

或者使用公用表表达式：

;with FirstCalcs as (
    Select t1.StartMile, t2.EndMile, t2.EndMile- t1.StartMile as TotMile 
    from 
    TableStarts as t1 
    inner join 
    TableEnds as t2 
    on t1.Id = t2.Id 
) 
select StartMile,EndMile,TotMile,TotMile+30 as EvenMoreMiles from FirstCalcs 

我通常喜欢使用的CTE如果将会有多个层次来构建最终的计算结果，否则大多数格式化方案都难以进行选择，子选择，子子选择等等，这些都很容易阅读。 CTE可以包括对以前定义的CTE的引用：

;with CTE1 as (
    SELECT ... 
), CTE2 as (
    SELECT ... FROM CTE1 
), CTE3 as (
    SELECT ... FROM CTE2 
), CTE4 as (
    SELECT ... FROM CTE2 ... CTE3 
) 
SELECT ... FROM CTE4 ... CTE1 

Answer 3

尝试使用派生表。

SELECT 
    DerivedTable.*, 
    TotMile + 30 as EvenMoreMiles 
From (Select 
     t1.StartMile, 
     t2.EndMile, 
     t2.EndMile- t1.StartMile as TotMile 
     FROM Table t1 
     Inner Join table2 t2 on t1.PK = t2.FK) DerivedTable 

Answer 4

您可以使用公用表表达式（CTE）来执行此操作。在这里地段：http://www.4guysfromrolla.com/webtech/071906-1.shtml

基本上，

CREATE VIEW ... AS 

WITH Mileage (StartMile, EndMile, TotMile) AS (Select t1.StartMile, t2.EndMile, t2.EndMile- t1.StartMile as TotMile 
from 
TableStarts as t1 
inner join 
TableEnds as t2 
on t1.Id = t2.Id) 

SELECT TotMile FROM Mileage