T-SQL JOIN contra una Expresión de tabla común (CTE)

Question

¿Es posible realizar una subconsulta JOIN contra una Expresión de tabla común? Si no, ¿alguien me puede decir cómo realizar lo que estoy tratando de hacer a continuación? Los ejemplos serían excelentes.

Por ejemplo:

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] 

Aquí está mi consulta completa:

;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) 

Gracias tanto!

Answer 1

Cuando define un CTE lo hace antes del resto de la consulta. Así que no se puede escribir:

LEFT JOIN (
    ;WITH CTE 
    ... 
) 

Como rápida a un lado, la razón personas ponen ; frente a WITH se debe a que todas las declaraciones anteriores necesitan ser terminados. Si los desarrolladores podían conseguir en el hábito de poner fin a todas las sentencias SQL con ; entonces no sería necesario, pero estoy divagando ...

Puede escribir varias CTE, así:

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

Answer 2

Puede tener múltiples CTE, creo; solo tienes que ponerlos a los dos en la parte superior.

Ver here:

Puede, sin embargo, definir múltiples CTE después de la palabra clave WITH separando cada CTE con una coma.

Answer 3

Si usted tiene múltiples CTE, tienen que estar al principio de su declaración (separada por comas, y sólo una ;WITH para iniciar la lista de CTE):

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

y entonces usted puede use ambos (o incluso más de dos) en su declaración SELECT.

Answer 4

Múltiple CTE debe declararse primero. Ejemplo:

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]