Question

1) A university database contains information about professors
(identified by emp_id) and courses (identified by course_id). Professors teach
courses. Each of the following situations concerns the Teaches relationship set.
For each situation, draw an ER diagram that describes it (assuming no further
constraints hold).
a) Professors can teach the same course in several semesters, and each offering
must be recorded.
b) Professors can teach the same course in several semesters, and only the most
recent such offering needs to be recorded. (Assume this condition applies in
all subsequent questions.)
c) Every professor must teach some course.
d) Every course is taught by exactly one professor (no more, no less).
e) Every professor teaches exactly one course (no more, no less), and every
course must be taught by at least one professor.
f) Suppose that certain courses can be taught by a team of professors jointly.
Model this situation by introducing additional entity sets and relationship
sets if necessary. Here, we assume that only the latest semester of a course
offering needs to be recorded

2) A company database needs to store information about employees
(identified by emp_num, with position, salary and phone as attributes),
departments (identified by dept_num, with dept_name and budget as attributes),
and children of employees (with name and age as attributes). Employees work in
departments; each department is managed by an employee; a child must be
identified uniquely by name when the parent (who is an employee; assume that
only one parent works for the company) is known. We are not interested in
information about a child once the parent leaves the company.
Draw an ER diagram that captures the above information.

Answer 1

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