Review Questions 1
1. Explain the following terms using examples:
a) Database
b) Database system
c) Database application
d) Database Management System
(DBMS)
e) Data Model
f) Metadata
g) Data Independence (logical and
physical)
2. Explain the difference between a file-based system and database system.
3. Explain the main components of a DBMS.
4. Discuss the importance of data modeling.
5. Discuss the basic differences between external schema, conceptual schema, and internal schema.
6. What is an entity set? Explain the difference between an entity and an entity set.
7. What is a relationship set? Explain the difference between a relationship instance and a
relationship set.
8. What is a participation role? When is it necessary to use role names in the description of
relationship types?
9. Under what conditions can an attribute of a binary relationship type be migrated to become an
attribute of one of the participating entity types?
10. Can an identifying relationship of a weak entity type be of degree greater than two? Give
examples to illustrate your answer.
11. Construct an ER diagram for a hospital with a set of patients and a set of medical doctors.
Associate with each patient a log of the various tests and examinations conducted.
12. Consider the following set of requirements for a university database that is used to keep track of
students’ transcripts.
a)
The university keeps track of each student’s name, IDNO, address, birthdate, sex, classs (1st year,
2nd year, etc), department, degree program (BSC, BIS, etc)
b) Each department is described by a name, department code, building number, phone, and Faculty.
Both name and department code have unique values for each department.
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c) Each course has course code, title, credit hours, level (level 200, 300, etc), and offering
department. The value of the course code is unique for each course.
d) Each instructor has IDNO, name, department, and title (lecturer, senior lecturer, etc). The value of
IDNO is unique for each instructor.
Draw an ER diagram for this application and indicate key attributes, cardinality constraints. Note any
unspecified requirements, and make appropriate assumptions to make the ER diagram complete.
Modify the above ER diagram so that you can be able to keep track of students’ result sheet.
13. You are given a relational database instance containing the following relations:
PART
SUPPLIER
Pno
p1
p2
p3
p4
p5
Sno
s1
s2
s3
s4
s5
Pname
nut
screw
washer
screw
hinge
Sname
John
Saul
Patel
Saul
John
City
Lobatse
Phikwe
Lobatse
Kanye
Hukuntsi
SUPPLY
Sno
s2
s1
s1
s2
s1
Pno
p4
p1
p3
p2
P2
Quantity
40
50
30
20
20
a. Give an example each of the relational concepts: Superkey, Candidate Key, Primary Key
and Foreign key. Briefly explain how these concepts are related.
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b. Express the request: “get the name of supplier, name of part, and quantity supplied for
supply involving supplier named John who supplied part named nut in quantity greater
than 40” as a sequence of Relational Algebra operations.
[5]
14. Explain the main distinction between an operational and non-operational (declarative) query
language.
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15. Suppose you have gathered the following database application requirements in respect of Micro
Lending Organization:
 The Micro Lending Organization is organized into branches. Each branch has a branch name, a city
it is located in and assets of the branch.
 The customers of the Micro Lending Organization have names, ids and an address.
 Customers also have accounts and may take loans.
 The Micro Lending Organization offers two types of accounts (savings and current accounts).
Accounts can be held by more than one customer and a customer can have many accounts.
 Each account has a balance and an account number. Each savings account has an interest rate
and each current account has an overdraft.
 Employees of the Micro Lending Organization have ids, names and telephone numbers.
 A loan originates at a particular branch and can be held by one or more customers.
 A loan has a loan number and loan amount.
 For each loan the Micro Lending Organization keeps track of the loan payment number uniquely
identifies a particular payment for a specific loan.
You are required to specify these requirements by means of suitable ER diagram.
[15]
OR
Represent the following E-R schema as tables. State any assumptions you make.
16. Consider the following relational schema:
STUDENT (stud-id, stud-name, age, address)
COURSE (c-code, c-name)
TAKING (stud-id, c-code, grade)
Write the following queries as relational algebra statements:
a) Get the names of students who are doing a course called CSI471 AND a course called CSI481.
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b) Get the names of students who are doing a course called CSI471 OR a course called CSI481.
[5]
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