What is the highest amount of difference between the ordered quantity and actual quantity received in a single purchase order and to which vendor was the purchase order made?
highest amount of difference between the ordered quantity and actual quantity received in a single purchase order refers to MAX(SUBTRACT(OrderQty, ReceivedQty));
SELECT T2.OrderQty - T2.ReceivedQty, VendorID FROM PurchaseOrderHeader AS T1 INNER JOIN PurchaseOrderDetail AS T2 ON T1.PurchaseOrderID = T2.PurchaseOrderID ORDER BY T2.OrderQty - T2.ReceivedQty DESC LIMIT 1