Relation Order Processing (Relasi Proses Pemesanan)

Consider the following six relations for an order processing database application in a company:

1. CUSTOMER(Cust#, Cname, City)
2. ORDER(Order#, Odate, Cust#, OrdAmt)
3. ORDER_ITEM(Order#, Item#, Qty)
4. ITEM(Item#, Unit_price)
5. SHIPMENT(Order#, Warehouse#, ShipDate)
6. WAREHOUSE(Warehouse#, City)

Here, OrdAmt refers to total dollar amount of an order, Odate is the date the order was placed and ShipDate is the date an order (or part of an order) is shipped from the warehouse. Assume that an order can be shipped from several warehouses. Specify the foreign keys for this schema, stating any assumptions you make. What other constraints can you think of for this database?