T-SQL: INSERT original value in OUTPUT clause

问题:

I have a table Items (ItemID, Name, ...) where ItemID is auto-generated identity

I want to add rows into this table FROM select on this same table. AND save into table variable the references between OriginalItemID and NewlyGeneratedID.

So I want it to look like the following:

DECLARE @ID2ID TABLE (OldItemID INT, NewItemID INT);

INSERT INTO Items OUTPUT Items.ItemID, INSERTED.ItemID INTO @ID2ID
SELECT * FROM Items WHERE Name = 'Cat';

BUT Items.ItemID obviously does not work here. Is there a workaround to make OUTPUT take original ItemID from the SELECT statement?

回答1:

If you are on SQL Server 2008+, you can use MERGE for getting both the current and the new ID. The technique is described in this question.

For your example the statement might look like this:

MERGE Items AS t
USING (
  SELECT *
  FROM Items
  WHERE Name = 'Cat'
) AS s
ON 0 = 1
WHEN NOT MATCHED BY TARGET THEN
  INSERT (target_column_list) VALUES (source_column_list)
OUTPUT INSERTED.ItemID, S.ItemID INTO @ID2ID (OldItemID, NewItemID);