Solution - Department of Informatics

5CCS02DB Database Systems
Lecturer: Sophia Tsoka
Teaching Assistants: Yiannis Siantos, Christos Hadjinikolis
October 14, 2013 – 3rd Tutorial Solutions
Exercise 1. Consider the following set of requirements for a university database that is used to
keep track of students transcripts.
• The university keeps track of each students name, student number, social security number,
current address and phone, permanent address and phone, birth date, gender, year of study
(1st year, 2nd year etc). Some user applications need to refer to the city, and post code
of the students permanent address, and to the students last name. Both social security
number and student number have unique values for each student.
• Each department is described by a name, department code, office number, office phone,
and college. Both name and code have unique values for each department.
• Each course has a course name, description, course number, number of semester hours,
level, and offering department. The value of course number is unique for each course.
Some courses may be offered by multiple departments (e.g. interdisciplinary courses).
• Each section has an instructor, semester, year, course, and section number. The section
number distinguishes different 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.
• Each section may be part of multiple courses.
course offering them
Sections are only identified through the
• Each student belongs to a major department and optionally to a minor department and is
following a single course (e.g. B.A. in Music, B.Sc. in Informatics etc).
Design an ER schema for this application, and draw an ER diagram for that 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.
On Page 2 you may find the updated solution. Note that since we have chosen to represent
cardinalities the way they are represented, then total participation relationships need to be
specified.
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Answer.
Current Phone
Permanent Phone
Student Number
Name
SSN
Build. Name/Number
Date Of Birth
Student
1
Major
Post Code
Current Address
Year
Address
Gender
1
1
Full Address
City
Country
Minor
Follows
N
2
N
Number
Semester
Level
CNumber
Phone
Name
N
Section
N
Course Section
N
Course
N
Offers
N
Department
Number
Year
Instructor
Name
Description
Hours
Office

Exercise 2. Convert the E-R diagram of exercise 1, from tutorial 2, to a relational database
schema.
State any key, entity, referential integrity, domain and semantic constraints that are applicable.
The domain constraints do not need to be precise (i.e. “String” is sufficient to specify that
something is a string, we do not need to specify maximum lengths at this point).
Answer. Entity Integrity Constraints: Entity Keys will be underlined. Relationship keys
are composite keys consisting of the primary key of each of the entities which participate in the
relationship.
Referential Integrity Constraints: Foreign Keys are Double Underlined. The way they
are named is < tableName > < attributeName >.
Domain Constraints: Will be specified next to each attribute name.
Semantic Constraints: Doctor.DOB, Patient.DOB, Contract.StartDate should all be past
dates.
Specialities should be actual doctor specialities (i.e. not just any string). We will also assume
that a doctor can have multiple specialities.
All the characters of Company.Phone and Pharmacy.Phone should be numbers with the
exception of the first character which may be “+”
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Patient
ID:Integer First Name:String Last Name:String DOB:Date Doctor SSN:Integer
Doctor
SSN:Integer First Name:String Last Name:String DOB:Date Start Date:Date
Doctor Speciality
Doctor SSN:Integer Speciality:Speciality String
Medicine
Name:String
Active Ingredient:String
Company
Name:String
Phone:String
Pharmacy
Name:String Phone:String Buiding Name-Number:String Post Code:String
Doctor Prescribes Medicine To Patient
Patient Id:Integer Doctor SSN:Integer Medicine Name:String
Pharmacy Sells Medicine
Pharmacy Name:String Medicine Name:String Price : Currency
Company Manufactures Medicine
Pharmacy Name:String Medicine Name:String
Pharmacy Contracts Company
Pharmacy Name:String Company Name:String Start Date:Date End Date:Date Contents:String
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