Database Reference
In-Depth Information
CustomerNumber
CustomerSoldToName
CustomerSoldToAddressLine1
CustomerSoldToAddressLine2
CustomerSoldToCity
CustomerSoldToState
CustomerSoldToZip
CustomerShipToName
CustomerShipToAddressLine1
CustomerShipToAddressLine2
CustomerShipToCity
CustomerShipToState
CustomerShipToZip
CustomerRepNumber
CustomerRepLastName
CustomerRepFirstName
206
ItemNumber
ItemDescription
ItemPrice
InvoiceNumber
InvoiceDate
CustomerNumber
OrderNumber
OrderDate
ShipDate
Freight
InvoiceTotal
InvoiceNumber, ItemNumber
ItemQuantityOrdered
ItemQuantityShipped
ItemQuantityBackordered
ItemAmount
FIGURE 6-16
Tentative list of functional dependencies for the Holt Distributors invoice
Based on your list of functional dependencies, you may learn that the shipping address for a given cus-
tomer will vary from one invoice to another. In other words, the shipping address depends on the invoice
number, not the customer number. A default shipping address may be defined for a given customer in case
no shipping address is entered with an order. However, the address that actually appears on the invoice
would depend on the invoice number. You may also determine that several columns actually depend on the
order that was initially entered. The order date, customer, shipping address, and quantities ordered on each
line of the invoice may have been entered as part of the initial order. At the time the invoice was printed,
additional information, such as the quantities shipped, the quantities back-ordered, and the freight charges,
may have been added. You may also find that the price is not necessarily the one stored with the item and
that the price can vary from one order to another. Given all these corrections, a revised list of functional
dependencies might look like Figure 6-17.
