1. COMP231 Tutorial 1
ER Model and ER to Relational Schema

2. E-R Diagram Rectangles – entity sets Ellipses – attributes
Diamonds – relationship sets
Double ellipses – multivalued attributes
Dashed ellipses – derived attributes
Double lines – total participation
Double rectangles – weak entity sets
Double diamonds – identifying relationship sets 2

3. Exercise 1.1 Construct E-R Diagram
A university registrar’s office maintains data about the following entities:
courses, including number, title, credits, syllabus, and prerequisites;
course offerings, including course number, year, semester, section number, instructor(s), timings, and classroom;
students, including student-id, name, and program;
instructors, including identification number, name, department, and title.
Further, the enrollment of students in courses and grades awarded to students in each course they are enrolled must be appropriately modeled.
Construct an E-R diagram for the registrar’s office.

4. Entities
course-offering
instructor
student
course

5. Course
“courses including number, title, credits, syllabus, and prerequisites”
Attribute?
Relationship?
courseno
credits
prerequisite
requires
course
maincourse
syllabus
title

6. Course Offering
“course offerings, including course number, year, semester, section number, instructor(s), timings, and classroom”
semester
time
courseno
course- offering
is_offered
room
course
secno
year

7. Weak Entity
A weak entity can only be identified uniquely by combining the primary key of another (owner) entity and the partial key of itself.
Owner entity set and weak entity set must participate in one-to-many relationship (one owner entity, many weak entities).
Weak entity set must have total participation in this identifying relationship set. 4

8. Student, Instructor
“students, including student-id, name, and program”
“instructors, including identification number, name, department, and title”
sid
name
iid
name
student
instructor
program
dept
title

9. Enrollment
“Further, the enrollment of students in courses and grades awarded to students in each course they are enrolled must be appropriately modeled.”
course-offering
enrolls
student
grade

10. Anymore?? Instructor teaches course….. course-offering instructor

11. E-R Diagram for a University

12. Exercise 1.2 Covert E-R Diagram into Tables

13. Entities (Not Weak)

14. Entities (Not Weak) course (courseno, title, syllabus, credits)
student (sid, name, program)
instructor (iid, name, dept, title)

15. Weak Entities

16. Weak Entities
course-offering (courseno, secno, year, semester, time, room)

17. Relationships (Not defining weak entities)

18. Relationships (Not defining weak entities)
enrolls (sid, courseno, secno, semester, year, grade)
teaches (courseno, secno, semester, year, iid)
requires (maincourse, prerequisite)

19. Relationships with Weak Entities

20. Relationships with Weak Entities
There is no extra table for the relationship between a weak entity and its strong entity.
The relationship is already present in the schema for the weak entity.
course-offering (courseno, secno, year, semester, time, room)

21. Relational Schemas for a University
course (courseno, title, syllabus, credits)
student (sid, name, program)
instructor (iid, name, dept, title)
course-offering (courseno, secno, year, semester, time, room)
enrolls (sid, courseno, secno, semester, year, grade)
teaches (courseno, secno, semester, year, iid)
requires (maincourse, prerequisite)

22. Submitted for – www.mycollegebag.in