SOLUTIONS TO REVIEW QUESTIONS AND EXERCISES: database systems a practical approach to design implementation and management 6th edition thomas connolly

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Database Systems
SOLUTIONS TO REVIEW QUESTIONS

AND EXERCISES

FOR PART 1 – BACKGROUND (CHAPTERS 1 – 3)
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,Database Systems: Instructor’s Guide - Part III


Solutions to Review Questions and Exercises


Chapter 1 Introduction to Databases............................................................................................ 3

Chapter 2 Database Environment ................................................................................................ 7

Chapter 3 Database Architectures and the Web ......................................................................... 11
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Chapter 1 Introduction to Databases

Review Questions

1.1 List four examples of database systems other than those listed in Section 1.1.


Some examples could be:

 A system that maintains component part details for a car manufacturer;
 An advertising company keeping details of all clients and adverts placed with them;
 A training company keeping course information and participants’ details;
 An organization maintaining all sales order information.


1.2 Discuss each of the following terms:
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Data For end users, this constitutes all the different values connected with the
various objects/entities that are of concern to them. See also Section 1.3.4.
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Database See Section 1.3.1
Database Management System See Section 1.3.2
Database Application Program See Section 1.3.3
Data Independence This is essentially the separation of underlying file structures from the
programs that operate on them, also called program-data independence. See
also Sections 1.2.2 and 1.3.1.
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Security The protection of the database from unauthorized users, which may involve
passwords and access restrictions. See also Section 1.6.
Integrity The maintenance of the validity and consistency of the database by use of
particular constraints that are applied to the data. See also Section 1.6.
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Views These present only a subset of the database that is of particular interest to a
user. Views can be customized, for example, field names may change, and
they also provide a level of security preventing users from seeing certain
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data. See also Section 1.3.3.


1.3 Describe the approach taken to the handling of data in the early file-based systems. Discuss the
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disadvantages of this approach.


Focus was on applications for which programs would be written, and all the data required would
be stored in a file or files owned by the programs. See also Section 1.2.


Clearly, each program was responsible for only its own data, which could be repeated in other
program’s data files. Different programs could be written in different languages, and would not be
able to access another program’s files. This would be true even for those programs written in the
same language, because a program needs to know the file structure before it can access it. See also
Section 1.2.2.


1.4 Describe the main characteristics of the database approach and contrast it with the file-based
approach.



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Focus is now on the data first, and then the applications. The structure of the data is now kept
separate from the programs that operate on the data. This is held in the system catalog or data
dictionary. Programs can now share data, which is no longer fragmented. There is also a reduction
in redundancy, and achievement of program-data independence. See also Section 1.3.


1.5 Describe the five components of the DBMS environment and discuss how they relate to each
other.


See Section 1.3.3.


1.6 Discuss the roles of the following personnel in the database environment:


Data Administrator See Section 1.4.1
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Database Administrator See Section 1.4.1
Logical Database Designer See Section 1.4.2
Physical Database Designer See Section 1.4.2
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Application Developer See Section 1.4.3
End-Users See Section 1.4.4


1.7 Discuss the three generations of DBMSs.


The CODASYL and hierarchical approaches represented the first generation of DBMSs. They
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were based on the concept that smaller components come together as parts of larger
components, and so on, until the final product is assembled. This structure, which conforms to
an upside down tree, is also known as a hierarchical structure.
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Relational DBMSs are referred to as second-generation DBMSs. In 1970, E. F. Codd of the
IBM Research Laboratory produced his highly influential paper on the relational data model
(“A relational model of data for large shared data banks,” Codd, 1970). This paper was very
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timely and addressed the disadvantages of the former approaches. Many experimental
relational DBMSs were implemented thereafter.
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In response to the increasing complexity of database applications, two “new” systems have
emerged: the object-oriented DBMS (OODBMS) and the object-relational DBMS
(ORDBMS). However, unlike previous models, the actual composition of these models is not
clear. This evolution represents third generation DBMSs.


1.8 Discuss the advantages and disadvantages of database management systems.


See Section 1.6




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