Database Systems 6th Edition by Ramez Elmasri, Shamkant B. Navathe

Exercise 4

Figure 7.31
-Consider the ER diagram in Figure 7.31. Assume that an employee may work in up to two departments or may not be assigned to any department. Assume that each department must have one and may have up to three phone numbers. Supply (min, max) constraints on this diagram. State clearly any additional assumptions you make. Under what conditions would the relationship HAS_PHONE be redundant in this example?