Discuss the difference between a composite key and a composite attribute. How would each be
indicated in an ERD?
A composite key is one that consists of more than one attribute. If the ER diagram contains the
attribute names for each of its entities, a composite key is indicated in the ER diagram by the fact that
more than one attribute name is underlined to indicate its participation in the primary key.
A composite attribute is one that can be subdivided to yield meaningful attributes for each of its
components. For example, the composite attribute CUS_NAME can be subdivided to yield the
CUS_FNAME, CUS_INITIAL, and CUS_LNAME attributes. There is no ER convention that enables
us to indicate that an attribute is a composite attribute.