ER Diagrams   «Prev  Next»

Resolving many-to-many relationships - Exercise

Objective: Convert a many-to-many relationship into two "one-to-many" relationships.

Exercise scoring


This exercise is worth a total of 30 points. You will receive up to 10 points for correctly creating each attribute of the composite entity as described below.

Background/overview

In the preceding lesson, you learned that many-to-many relationships are resolved by breaking down each M:N relationship into two 1:N relationships. This is achieved by creating a composite entity whose only function is to represent the link between the other two entities. You also learned that the composite entity has no key attribute of its own; rather, it accepts the key attributes from the other two entities to form a composite key attribute.

Instructions

The Stories on CD case study has one many-to-many relationship: the ORDER:CD relationship. Your task is to resolve the ORDER:CD relationship. The two entities are illustrated below, complete with the attributes you will need to complete this exercise.

Two Entities ORDER and CD

Please name the composite entity you create LINE ITEM. Your answer should be in the following format:
ORDER
attribute
attribute
etc.

LINE ITEM
attribute
attribute
etc.

CD
attribute
attribute
etc.

Hints

When a composite entity is created to link two other entities, it sometimes makes sense to move some non-key attributes out of the other two entities and into the composite entity. Keep this in mind when you populate the composite entity with attributes.

Submitting your exercise

Type or paste your answers into the text box below, then click Submit to submit your result and view a results page.