Starting model
In Stories on CD, an order may contain several CD titles and a CD title may appear on many orders.
Initial attributes before resolving ORDER:CD.Assume at most one line per CD title in an order, a positive quantity per line, an agreed total LineCost per line, and one ShipDate per line (unknown until shipped). Multiple shipments of one line are outside this exercise. RetailPrice is the current catalog price, which may change; LineCost preserves the agreed line amount.
Task
Create an associative entity named LINE ITEM. List the attributes remaining in ORDER and CD and those in LINE ITEM. Identify primary and foreign keys. Move Quantity, LineCost and ShipDate to their proper entity and explain each placement. A schema outline is sufficient; SQL is not required.
The associative entity needs a key. Under the stated one-line-per-CD-per-order rule, (OrderNo, CDNo) can be its composite primary key.
Self-assessment: 30 points
Award up to 10 points per attribute for Quantity, LineCost and ShipDate: 5 for placement in LINE ITEM and 5 for a matching line-specific explanation. Total: 30 points. Also check the two foreign keys, line key and unchanged parent attributes against the model. The page displays a model answer; it does not automatically grade free text.