मेरी राय में यह MERGE और आउटपुट का बहुत अच्छा उपयोग है। मैंने कई परिदृश्यों में उपयोग किया है और आज तक किसी भी विषमता का अनुभव नहीं किया है। उदाहरण के लिए, यहां परीक्षण सेटअप है जो एक फ़ोल्डर और सभी फ़ाइलों (पहचान) को एक नए बनाए गए फ़ोल्डर (गाइड) में क्लोन करता है।
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