平等命令寫入兩次 - 一次工作，沒有第二次

Question

這是我的T-SQL代碼：

;with tmpFolderPermissions(fp_folder, DataItem, fp_modify) as 
(
    select 
     fp_folder, LEFT(fp_modify, CHARINDEX(',',fp_modify+',')-1), 
     STUFF(fp_modify, 1, CHARINDEX(',',fp_modify+','), '') 
    from dbo.tblFolderPermissions 

    union all 

    select 
     fp_folder, CAST (LEFT(fp_modify, CHARINDEX(',', fp_modify+',') -1) AS VARCHAR(200)), 
     STUFF(fp_modify, 1, CHARINDEX(',',fp_modify+','), '') 
    from tmpFolderPermissions 
    where fp_modify > '' 
) 
select fp_folder, DataItem 
from tmpFolderPermissions 

，它工作正常，結果我得到一個表約200行。但是，如果用上面那個完整的代碼我添加與上述相同的命令：

select fp_folder, DataItem 
from tmpFolderPermissions 

所以基本上，如果我連續寫了兩次，第一個命令顯示了我200個結果，這是很好的，但第二個給我這個錯誤：

Invalid object name 'tmpFolderPermissions'.

爲什麼它給我一個錯誤，當它執行一個毫秒前？

Answer 1

tmpFolderPermissions是CTE。 CTE不能在多個查詢中重用，因爲它是查詢本身的一部分。所以第二次調用它時，它不存在。 改爲使用臨時表或視圖。從鏈接

報價：

A common table expression (CTE) can be thought of as a temporary result set that is defined within the execution scope of a single SELECT, INSERT, UPDATE, DELETE, or CREATE VIEW statement. A CTE is similar to a derived table in that it is not stored as an object and lasts only for the duration of the query.

Answer 2

這是因爲tmpFolderPermissions是CTE，CTE爲某事像tmp目錄表，它不是來自外部訪問的查詢。如果你想重新使用這些數據，你應該將其保存到tmp下表

;with tmpFolderPermissions(fp_folder, DataItem, fp_modify) as 
(
    select 
     fp_folder, LEFT(fp_modify, CHARINDEX(',',fp_modify+',')-1), 
     STUFF(fp_modify, 1, CHARINDEX(',',fp_modify+','), '') 
    from dbo.tblFolderPermissions 

    union all 

    select 
     fp_folder, CAST (LEFT(fp_modify, CHARINDEX(',', fp_modify+',') -1) AS VARCHAR(200)), 
     STUFF(fp_modify, 1, CHARINDEX(',',fp_modify+','), '') 
    from tmpFolderPermissions 
    where fp_modify > '' 
) 
select fp_folder, DataItem into #tmpFolderPermissions 
from tmpFolderPermissions 

，然後#tmpFolderPermissions查詢