2.2

Consider the foreign-key constraint from the dept_name attribute of instructor to the department relation. Give examples of inserts and deletes to these relations that can cause a violation of the foreign-key constraint.

• Insert a tuple
  (10111, Ostrom, Economics, 110000)
  into the instructor table, where the department table does not have the department Economics, would violate the foreign-key constraint. (Refer Figure 2.4 and Figure 2.5 for the instances of the relation instructor and department).

• Delete the tuple
  (Biology, Watson, 90000)
  from the department table, where at least one student or instructor tuple has dept_name as Biology, would violate the foreign-key constraint.