1. What two conditions must be met before an entity can be classified as a weak entity? Give an example of a weak entity.
2. What is a strong (or identifying) relationship, and how is it depicted in a Crow's Foot ERD?
3. Briefly, but precisely, explain the difference between single-valued attributes and simple attributes. Give an example of each.
4. What is a multivalued attribute? Give an example.
5. Given the business rule "an employee may have many degrees," discuss its effect on attributes, entities, and relationships. (Hint: Remember what a multivalued attribute is and how it might be implemented.)
6. What is a recursive relationship? Given an example.
7. How would you (graphically) identify each of the following ERM components in a Crow's Foot ER model (describe and provide a graphical example of each)?
a. an entity
b. the cardinality (all)
c. a weak relationship
d. a strong relationship
8. Discuss the difference between a composite key and a composite attribute. How would each be indicated in an ERD?
9. Create the Crow's Foot ERD using Visio (copy/paste diagram into your Word document) depicting the data model which adheres to the business rules listed below. Include all appropriate attributes, keys (primary and foreign), relationships, connectivities (cardinalities).
a. A department employs many employees, but each employee is employed by one department.
b. Some employees, known as "rovers," are not assigned to any department.
c. A division operates many departments, but each department is operated by one division.
d. An employee may be assigned many projects, and a project may have many employees assigned to it.
e. A project must have at least one employee assigned to it.
f. One of the employees manages each department, and each department is managed by only one employee.
g. One of the employees runs each division, and each division is run by only one employee.