Question

Consider the following set of requirements for a UNIVERSITY database that is used to keep track of students’ transcripts. This is similar but not identical to the database shown in Figure 1.2:

a. The university keeps track of each student’s name, student number, Social Security number, current address and phone number, permanent address and phone number, birth date, sex, class (freshman, sophomore, ..., graduate), major department, minor department (if any), and degree program (B.A., B.S., ..., Ph.D.). Some user applications need to refer to the city, state, and ZIP Code of the student’s permanent address and to the student’s last name. Both Social Security number and student number have unique values for each student.

b. Each department is described by a name, department code, office number, office number, and college. Both name and code have unique values for each department.

c. Each course has a course name, description, course number, number of semester hours, level, and offering department. The value of the course number is unique for each course.

d. Each section has an instructor, semester, year, course, and section number. The section number distinguishes sections of the same course that are taught during the same semester/year; its values are 1, 2, 3, ..., up to the number of sections taught during each semester.

e. A grade report has a student, section, letter grade, and numeric grade (0, 1, 2, 3, 4 for F, D, C, B, A, respectively).

Design an ER schema for this application, and draw an ER diagram for the schema. Specify key attributes of each entity type, and structural constraints on each relationship type. Note any unspecified requirements, and make appropriate assumptions to make the specification complete.

Answer 1

ER diagram is given below. Note Entities are rectangle, Relationship are diamond and Attributes are oval. Key attributes are underlined, partial key have dotted underline. Composite attributes have attributes of themselves, Derived attributes have dotted boundry. Double line to Relation define total participation, single line means partial. Modality and Cardinality are defined on both side of Relationships.

All needed info of Student, Department, Course, Section, Grade Report is stored as attributes or Relationship as per Question Specification. Major and minor department of student are stored as Relationship between the two entities. We assume a student must have one and only one major department while a department must have atleast one student taking it as major department. Minor department is same but is optional from both Student and Department side. Offering Department of Course is stored as Relation - Assumption is each course must have one offering department only and a department must offer atleast one course. Same goes for course of Section - A section must belong to one course only while a course must have at least one section. Note that section is a weak entity dependent on course - Section_Number is just a partial key. Grade report become a relationship between student and section (optional from both sides as new students and recently started sections may not have any data here) with cardinality assumption that a student may have multiple grade report for multiple section while a section may have multiple report for multiple students. Numeric grade here is derived from letter grade.