Question

I have two tables:
Folder, Files.
Each table has 4 fields:
ParentID, ID, Name, Type

I need to create a CTE in order to retrieve the entire tree in one shot, using T-SQL.
So far this is what I have done, but the recursion is not active yet.

I forgot to mention that inside a folder there may be one or more folders/files.

Answer 1

Assuming that you’re using NULL for the ParentID items in the root the following should work:

WITH FilesAndFolders AS (
    SELECT ID AS FileID, 
           CAST(NULL AS int) AS FolderID, 
           ParentID, 
           Name, 
           [Type]
    FROM File
    UNION ALL
    SELECT CAST(NULL AS int),
           ID, 
           ParentID, 
           Name, 
           [Type]
    FROM Folder
),
Tree AS (
    SELECT FileID, 
           FolderID, 
           Name, 
           [Type], 
           CAST('' AS nvarchar(MAX)) AS [Path]
    FROM FilesAndFolders
    WHERE ParentID IS NULL
    UNION ALL 
    SELECT FF.FileID, 
           FF.FolderID, 
           FF.Name, 
           FF.[Type], 
           T.[Path]+T.[Name]+'/'
    FROM FilesAndFolders FF
    JOIN Tree T ON T.FolderID = FF.ParentID
)
SELECT FileID, FolderID, [Path]+[Name] FullName, [Type]
FROM Tree