A Query for MERGE with CASE in UPDATE (T-SQL)

-- DELETES THE DUPLICATES IF ANY! (THIS IS A MUST WHEN YOU USE MERGE)
DELETE everything FROM (
SELECT *, rownum = ROW_NUMBER() OVER (PARTITION BY ItemID ORDER BY ItemID)
FROM QuantityUpdates
) everything
WHERE rownum > 1;
 
-- please notice that you can also use group by to prevent duplicate rows !!!
 
MERGE INTO
Products AS Prod
USING
QuantityUpdates AS Qty
ON
Prod.ItemID = Qty.ItemID
WHEN
MATCHED
THEN UPDATE SET
QtyInStock = Qty.QtyInStock,
UpdatedDateStamp = GETDATE(),
Discontinued = CASE WHEN Qty.QtyInStock > 0 THEN 0 ELSE 1 END;