針對公用表表達式（CTE）的T-SQL JOIN

Question

是否可以針對公用表表達式執行JOIN子查詢？如果沒有，那麼有人可以讓我知道如何執行我在下面嘗試做的事情？例子會很好。

例如：

LEFT JOIN (

      ;WITH [UserDefined] 
       AS (SELECT *, -- Make sure we get only the latest revision. 
         ROW_NUMBER() OVER (PARTITION BY [ID] 
               ORDER BY [RevisionNumber] DESC) AS RN 
        FROM [syn_Change]) 

      SELECT [UserDefined].[ID] 
       ,[UserDefined].[ChangeNumber] 
       ,[UserDefined].[Usr_CoResponsibility] 
       ,[UserDefined].[Usr_StarFlowStatus] 

      FROM [UserDefined] 
      WHERE (RN = 1) 

      ) [UserColumns] 
ON [UserColumns].[ChangeNumber] = [CTE].[ChangeNumber] 

這裏是我完整的查詢：

;WITH CTE 
    AS (SELECT *, -- Make sure we get only the latest revision. 
      ROW_NUMBER() OVER (PARTITION BY [ItemID] 
            ORDER BY [RevisionNumber] DESC) AS RN 
     FROM [dw_Change]) 

SELECT [CTE].[ItemID] 
     ,[CTE].[ViewID] 
     ,[CTE].[FolderItemID] 
     ,[CTE].[RevisionNumber] 
     ,[CTE].[ChangeNumber] 
     ,[CTE].[Synopsis] 
     ,[CTE].[Description] 
     ,[CTE].[EnteredOn] 
     ,[CTE].[Responsibility] 
     --,[UserColumns].[Usr_CoResponsibility] 
     --,[UserColumns].[Usr_StarFlowStatus] 
     ,[CTE].[Status] -- This will display the human name on the front-end with code. 
     ,[Users].[F7] AS [ResponsibilityName] 
     ,[GroupName].[Name] AS [AppGroupName] 
     ,[AppName].[Name] AS [AppName] 
FROM CTE 
LEFT JOIN [S3] [Users] ON [Users].[F0] = [CTE].[Responsibility] 
LEFT JOIN (SELECT [Name], [ViewID] 
      FROM [dw_Folder] 
      WHERE ([FolderItemID] = -1)) [GroupName] 
ON [GroupName].[ViewID] = [CTE].[ViewID] 

LEFT JOIN (SELECT [Name], [ItemID] 
      FROM [dw_Folder] 
      WHERE ([FolderItemID] <> -1)) [AppName] 
ON [AppName].[ItemID] = [CTE].[FolderItemID] 

LEFT JOIN (

      ;WITH [UserDefined] 
       AS (SELECT *, -- Make sure we get only the latest revision. 
         ROW_NUMBER() OVER (PARTITION BY [ID] 
               ORDER BY [RevisionNumber] DESC) AS RN 
        FROM [syn_Change]) 

      SELECT [UserDefined].[ID] 
       ,[UserDefined].[ChangeNumber] 
       ,[UserDefined].[Usr_CoResponsibility] 
       ,[UserDefined].[Usr_StarFlowStatus] 

      FROM [UserDefined] 
      WHERE (RN = 1) 

      ) [UserColumns] 
ON [UserColumns].[ChangeNumber] = [CTE].[ChangeNumber] 

WHERE (RN = 1) 

非常感謝！

Answer 1

當你定義一個CTE時，你會在查詢的其餘部分之前這麼做。所以你不能寫：

LEFT JOIN (
    ;WITH CTE 
    ... 
) 

作爲一個快速不談，原因人把;在WITH前面是因爲先前所有的語句需要被終止。如果開發人員可以得到終止與;那麼就沒有必要所有SQL語句的習慣，但我離題...

您可以編寫多個熱膨脹係數，像這樣：

WITH SomeCTE AS (
    SELECT ... 
    FROM ... 
), AnotherCTE AS (
    SELECT ... 
    FROM ... 
) 
SELECT * 
FROM SomeCTE LEFT JOIN 
    AnotherCTE ON ... 
; 

Answer 2

我相信你可以有多個CTE;你只需要把它們放在最上面。

見here：

你可以，但是，在每個CTE用逗號分隔定義多個CTE的WITH關鍵字。

Answer 3

如果您有多個CTE的，他們需要的是在你的語句開頭（以逗號分隔，且只有一個;WITH開始CTE的列表）：

;WITH CTE AS (......), 
[UserDefined] AS (.......) 
SELECT..... 

，然後你可以在您的SELECT聲明中同時使用（或甚至超過兩個）。

Answer 4

需要首先聲明多個CTE。例如：

WITH CTE_1 AS 
(
    .... 
), 
CTE_2 AS 
(
    ... 
) 

SELECT  * 
FROM   FOO 
LEFT JOIN  CTE_1 
LEFT JOIN  CTE_2 

Answer 5

; 
WITH 
    RANKED_CTE AS 
(
    SELECT 
    *, 
    ROW_NUMBER() OVER (PARTITION BY [ItemID] ORDER BY [RevisionNumber] DESC) AS RN 
    FROM 
    [dw_Change] 
) 
, 
    CTE AS 
(
    SELECT 
    * 
    FROM 
    RANKED_CTE 
    WHERE 
    RN = 1 
) 
, 
    GroupName AS 
(
    SELECT 
    [Name], [ViewID] 
    FROM 
    [dw_Folder] 
    WHERE 
    ([FolderItemID] = -1) 
) 
, 
    AppName AS 
(
    SELECT 
    [Name], [ItemID] 
    FROM 
    [dw_Folder] 
    WHERE 
    ([FolderItemID] <> -1) 
) 
SELECT [CTE].[ItemID] 
     ,[CTE].[ViewID] 
     ,[CTE].[FolderItemID] 
     ,[CTE].[RevisionNumber] 
     ,[CTE].[ChangeNumber] 
     ,[CTE].[Synopsis] 
     ,[CTE].[Description] 
     ,[CTE].[EnteredOn] 
     ,[CTE].[Responsibility] 
     --,[UserColumns].[Usr_CoResponsibility] 
     --,[UserColumns].[Usr_StarFlowStatus] 
     ,[CTE].[Status] -- This will display the human name on the front-end with code. 
     ,[Users].[F7] AS [ResponsibilityName] 
     ,[GroupName].[Name] AS [AppGroupName] 
     ,[AppName].[Name] AS [AppName] 
FROM 
      CTE 
LEFT JOIN [S3] [Users] ON [Users].[F0] = [CTE].[Responsibility] 
LEFT JOIN [GroupName] ON [GroupName].[ViewID] = [CTE].[ViewID] 
LEFT JOIN [AppName]  ON [AppName].[ItemID] = [CTE].[FolderItemID]