Example Relational Scheme
student (rollNo, name, degree, year, sex, deptNo, advisor)
department (deptId, name, hod, phone)
professor (empId, name, sex, startYear, deptNo, phone)
course (courseId, cname, credits, deptNo)
enrollment (rollNo, courseId, sem, year, grade)
teaching (empId, courseId, sem, year, classRoom)
preRequisite (preReqCourse, courseID)
Question:
Determine the students who are enrolled for every
course taught by Prof Ramanujam. Assume that Prof
Ramanujam teaches at least one course.
Answer:
1. {s.rollNo | student (s) ^
2. (∀c)(course (c) ^
3. ((∃t),(∃p)( teaching(t) ^ professor(p) ^
4. t.courseId = c.courseId ^
5. p.name = “Ramanujam” ^
6. p.empId = t.empId )) →
7. (∃e) (enrollment(e) ^
8. e.courseId = c.courseId ^
9. e.rollNo = s.rollNo)
10. )
11. }
Please explain the answer, i am little bit confused with how relation calculus express divide operator.
(My belief if that ∀ is similar to the quotient operator. ) TIA !