Example of MERGE in SQL Server 2008
MERGE Production.ProductInventory AS [pi]
USING (
SELECT ProductID,
SUM(OrderQty) AS OrderQty
FROM Sales.SalesOrderDetail AS sod
INNER JOIN Sales.SalesOrderHeader AS soh ON sod.SalesOrderID = soh.SalesOrderID
WHERE soh.OrderDate = GETDATE()
GROUP BY ProductID
) AS src (ProductID, OrderQty) ON src.ProductID = [pi].ProductID
WHEN MATCHED AND src.OrderQty = 0
THEN DELETE;
WHEN MATCHED
THEN UPDATE SET [pi].Quantity = src.OrderQty
WHEN NOT MATCHED
THEN INSERT VALUES (src.ProductID, src.OrderQty)
