Verwenden von merge..output, um eine Zuordnung zwischen source.id und target.id zu erhalten

Meiner Meinung nach ist dies eine großartige Verwendung von MERGE und Ausgabe. Ich habe es in mehreren Szenarien verwendet und bisher keine Kuriositäten festgestellt. Hier ist zum Beispiel ein Testaufbau, der einen Ordner und alle darin enthaltenen Dateien (Identität) in einen neu erstellten Ordner (GUID) klont.

DECLARE @FolderIndex TABLE (FolderId UNIQUEIDENTIFIER PRIMARY KEY, FolderName varchar(25));
INSERT INTO @FolderIndex 
    (FolderId, FolderName)
    VALUES(newid(), 'OriginalFolder');

DECLARE @FileIndex TABLE (FileId int identity(1,1) PRIMARY KEY, FileName varchar(10));
INSERT INTO @FileIndex 
    (FileName)
    VALUES('test.txt');

DECLARE @FileFolder TABLE (FolderId UNIQUEIDENTIFIER, FileId int, PRIMARY KEY(FolderId, FileId));
INSERT INTO @FileFolder 
    (FolderId, FileId)
    SELECT  FolderId, 
            FileId
    FROM    @FolderIndex
    CROSS JOIN  @FileIndex;  -- just to illustrate

DECLARE @sFolder TABLE (FromFolderId UNIQUEIDENTIFIER, ToFolderId UNIQUEIDENTIFIER);
DECLARE @sFile TABLE (FromFileId int, ToFileId int);

-- copy Folder Structure
MERGE @FolderIndex fi
USING   (   SELECT  1 [Dummy],
                    FolderId, 
                    FolderName
            FROM    @FolderIndex [fi]
            WHERE   FolderName = 'OriginalFolder'
        ) d ON  d.Dummy = 0
WHEN NOT MATCHED 
THEN INSERT 
    (FolderId, FolderName)
    VALUES (newid(), 'copy_'+FolderName)
OUTPUT  d.FolderId,
        INSERTED.FolderId
INTO    @sFolder (FromFolderId, toFolderId);

-- copy File structure
MERGE   @FileIndex fi
USING   (   SELECT  1 [Dummy],
                    fi.FileId, 
                    fi.[FileName]
            FROM    @FileIndex fi
            INNER
            JOIN    @FileFolder fm ON 
                    fi.FileId = fm.FileId
            INNER
            JOIN    @FolderIndex fo ON 
                    fm.FolderId = fo.FolderId
            WHERE   fo.FolderName = 'OriginalFolder'
        ) d ON  d.Dummy = 0
WHEN NOT MATCHED 
THEN INSERT ([FileName])
    VALUES ([FileName])
OUTPUT  d.FileId,
        INSERTED.FileId
INTO    @sFile (FromFileId, toFileId);

-- link new files to Folders
INSERT INTO @FileFolder (FileId, FolderId)
    SELECT  sfi.toFileId, sfo.toFolderId
    FROM    @FileFolder fm
    INNER
    JOIN    @sFile sfi ON  
            fm.FileId = sfi.FromFileId
    INNER
    JOIN    @sFolder sfo ON 
            fm.FolderId = sfo.FromFolderId
-- return    
SELECT  * 
FROM    @FileIndex fi 
JOIN    @FileFolder ff ON  
        fi.FileId = ff.FileId 
JOIN    @FolderIndex fo ON  
        ff.FolderId = fo.FolderId