Chapter 2: Database System Concepts and Architecture
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CHAPTER 2: DATABASE SYSTEM CONCEPTS AND ARCHITECTURE
Answers to Selected Exercises
2.12 – Think of different users for the database of Figure 1.2. What type of applications would
each user need? To which user category would each belong and what type of interface
would they need?
Answer:
(a) Registration Office User: They can enter data that reflect the registration of students in
sections of courses, and later enter the grades of the students. Applications can include:
– Register a student in a section of a course
– Check whether a student who is registered in a course has the appropriate prerequisite
2.13 – No solution provided.
2.14 – if you were designing a Web-based system to make airline reservations and to sell
airline tickets, which DBMS Architecture would you choose from Section 2.5? Why? Why
would the other architectures not be a good choice?
Answer:
2.5.4 Three-Tier Client/Server Architecture for Web Application is the best choice. The Client
2.5.1 Centralized DBMS Architecture would not work since the user interface and database
2.5.2 Basic Client/Server Architecture and 2.5.3 Two-Tier Client/Server Architecture would
work if the Business Logic can reside on server other than the DBMS Server. In general, if
2.15 – Consider Figure 2.1. In addition to constraints relating the values of columns in one
table to columns in another table, there are also constraints that impose restrictions on
Chapter 2: Database System Concepts and Architecture
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values in a column or a combination of columns within a table. One such constraint forces
that a column or a group of columns must be unique across all rows in the table. For
example, in the STUDENT table, the StudentNumber column must be unique (to prevent two
different students from having the same StudentNumber). Identify the column or the group
of columns in the other tables that must be unique across all rows in the table?
Answer:
Table
Column(s)
COURSE
CourseNumber
Since this contains the combination of the department and the number
that must be unique within the department. Note we will overlook the
fact this does not accommodate a department from offering several
“Special Topics” course with the same CourseNumber but different
titles. We could make this a combination of CourseNumber and
CourseName, but this is more succeptible to someone mistyping while
entering data.
PREREQUISITE
The combination of CourseNumber and PrerequisiteNumber
SECTION
SectionIdentifier
We assume that no two sections can have the same SectionIdentifier.
If we were to consider that SectionIdentifier is unique only within a
given course offered in a given term (such as section 2 of CS101)
then the answer changes to the combination of SectionIdentifier,
CourseNumber, Semester, and Year.
GRADE_REPORT
StudentNumber and SectionIdentifier
As per assumption stated in SECTION, the SectionIdentifier will be
different if a student takes the same course or a different course in
another term.