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Concepts of Database Management System 1st Edition
Shefali Naik Digital Instant Download
Author(s): Shefali Naik
ISBN(s): 9789332537231, 9332537232
Edition: 1
File Details: PDF, 8.53 MB
Year: 2014
Language: english

CONCEPTS OF
DATABASE
MANAGEMENT
SYSTEM___
_ _ _ _ _ _ SHEFALI NAIK
ALWAYS LEARN I NG PEARSON

Concepts of Database
Management System
Shefali Naik
FM_Final.indd 1 3/18/2014 5:02:47 PM

Dedicated to
My husband Trushit, daughter Jisha, and son Harsheev
FM_Final.indd 2 3/18/2014 5:02:47 PM
Copyright © 2014 Dorling Kindersley (India) Pvt. Ltd.
No part of this eBook may be used or reproduced in any manner whatsoever without the
publisher’s prior written consent.
This eBook may or may not include all assets that were part of the print version. The
publisher reserves the right to remove any material in this eBook at any time.
10 9 8 7 6 5 4 3 2 1
Head Office: 7th Floor, Knowledge Boulevard, A-8(A) Sector 62, Noida 201 309, India.
Registered Office: 11 Community Centre, Panchsheel Park, New Delhi 110 017, India.
ISBN: 9789332526280
e-ISBN: 9789332537231

Contents
Foreword vii
Preface ix
Acknowledgements xi
About the Author xiii
Chapter 1 Basics of Database 1
1.1 Introduction 1
1.2 Data and Information 1
1.2.1 Data 1
1.2.2 Information 2
1.3 Database 5
1.3.1 Components of Database System 6
1.4 Database Management 11
1.5 Database Management System 11
1.6 Need for a Database 12
1.7 File-based Data Management System 12
1.8 Characteristics, or Features, or Advantages
of Database Systems 14
1.9 Limitations of Database 15
Summary 16
Chapter 2 Data Models and Architecture of DBMS 19
2.1 Evolution of Data Models 19
2.2 Hierarchical Data Model 21
2.3 Network Data Model 26
2.4 Relational Data Model 27
2.5 Object-oriented Data Model 30
2.6 Object-relational Data Model 32
2.7 Three Level Architecture of Database 33
2.8 Database Languages 35
2.9 Data and Structural Independence 36
Summary 36
Chapter 3 Relational Database Management System 41
3.1 Introduction 41
3.2 RDBMS Terminology 41
3.3 Various Types of Keys 44
3.4 Integrity Rules 48
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iv | Contents
3.5 Relational Set Operators 50
3.6 Retrieval Operators 52
3.7 CODD’s Twelve Rules of Relational Database 53
3.8 Database Life Cycle 54
3.9 Data Dictionary 54
Summary 55
Chapter 4 Developing Entity-Relationship Diagram 59
4.1 Introduction 59
4.2 Identifying Entities 60
4.3 Identifying Relationships 63
4.4 Types of Relationships 63
4.5 Relationship Participation 66
4.6 Strong and Weak Relationship 68
4.7 Managing Many-to-many Relationship 68
4.8 Example of E-R Model 68
4.9 Extended E-R Model 72
4.10 Converting E-R Model into Relational Model 73
4.11 Object Modelling 75
4.11.1 Subclass and Superclass 75
4.11.2 Specialization and Generalization 76
4.11.3 Class Diagram 76
Summary 76
Chapter 5 Normalization82
5.1 Introduction 82
5.2 Need for Normalization 82
5.3 Types of Dependencies 83
5.4 First Normal Form 88
5.5 Second Normal Form 88
5.6 Third Normal Form 94
5.7 Boyce-Codd Normal Form 96
5.8 Multi-valued Dependency 98
5.9 Join Dependency 100
5.10 Lossless and Lossy Decompositions 101
5.11 Normalizing Tables 102
5.12 Examples 103
Summary 108
Chapter 6 Managing Data Using Structured Query Language (SQL) 111
6.1 Introduction 111
6.2 Data Definition Commands 112
6.3 Data Manipulation Commands 114
6.4 SELECT Statement and Its Clauses 115
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Contents | v
6.5 Aggregate Functions 118
6.6 Date and Time Functions 119
6.7 String Functions 121
6.8 Conversion Functions 122
6.9 Mathematical Functions 122
6.10 Special Operators 123
6.11 Types of Constraints 125
6.12 Types of Join and Set Operators 127
6.13 Sub-query 128
6.14 Advances SQL Roll-up, Cube, Crosstab 129
Summary 132
Chapter 7 Introduction to PL/SQL 138
7.2 Block of PL/SQL in Oracle 138
7.3 Cursors in Oracle 139
7.4 Procedures in Oracle 142
7.5 Functions in Oracle 143
7.6 Triggers in Oracle 144
7.7 Overview of Packages in Oracle 145
Summary 146
Chapter 8 Transaction Management in Database 148
8.2 Definition of Transaction 148
8.3 Properties of Transaction 152
8.4 States of Transaction 155
8.5 Concurrency Control Using Locks 155
8.6 Deadlocks 158
8.7 Database Backup and Recovery 159
8.8 Security, Integrity and Authorization 161
Summary 161
Chapter 9
Centralized and Distributed Database
Management System 165
9.2 Types of Databases 165
9.3 Centralized Database Management System
vs. Distributed Database Management System 166
9.4 DDBMS Components 169
9.5 Distributed Processing 169
9.6 DDBMS Advantages and Disadvantages 170
Summary 170
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vi | Contents
Chapter 10 Advancement in Databases 172
10.1 Multidimensional Database 172
10.2 Mobile Databases 172
10.3 Multimedia Databases 174
10.4 Data Warehousing and Data Mining 174
10.5 Open Source Database 175
10.6 Spatial Databases 175
10.7 Moving Object Databases 176
10.8 NoSQL Database 176
Summary 177
Chapter 11 Overview of MS-Access 2007 180
11.1 MS-Access as an RDBMS 180
11.2 Elements of MS-Access 180
11.3 Creating Database and Tables 181
11.4 Data Types of MS-Access 183
11.5 Sorting and Filtering Records in MS-Access 187
11.6 Creating Queries in MS-Access 188
11.7 Creating Forms in MS-Access 196
11.8 Creating Reports in MS-Access 201
11.9 Creating Macros and Switchboard 205
Summary 211
Chapter 12 Overview of Oracle 221
12.1 Oracle as an RDBMS 221
12.2 Logging into Oracle 221
12.3 Command Summary of Oracle Database 10g XE 222
12.4 Database Administration 228
12.4.1 Managing Users 228
12.4.2 Managing Roles 229
12.4.3 Managing Privileges 231
Summary 233
References and Bibliography 235
Index 243
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Foreword
Database Management System is one of the most important subjects of the computer and IT
field. It is used in almost all the applications like management information systems, expert
systems, business information systems, mobile applications, and many more. Over the years, the
world has witnessed many inventions in database technologies. The most important invention
is relational database management system. Application developers, in the IT industry, are using
relational model-based databases for more than thirty years.
Students of IT, computer science and applications, are required to learn databases in one or more
courses. Databases are used to store and retrieve data. There are certain rules used to manage data
within a database. Database provides many features related to data, such as sharing and integration
of data, consistent transaction execution, security and recovery of data through authorization and
algorithms. The relational models use a common language, named as Structured Query Language
(SQL) to process data. With the rise of the Internet and mobile technologies, databases are also
evolving. To store huge amount of data which are spreading worldwide on the Internet and mobile
devices, relational database management systems are not enough. Special types of databases, such
as NoSQL (Not only SQL) are required for managing such data.Apart from NoSQL databases, the
databases which are able to store information related to moving objects, multimedia data, historical
data from multiple dimensions, spatial data, etc., are also needed. Automation of processes also
require maintenance of the existing applications and analysis of historical data. Analysis of histori-
cal data helps in improving business functions by taking important decisions.
In this book, the concepts of databases has been clearly explained giving examples in a lucid
language. All chapters are well-organized and comprehensively covering the syllabus of the
course on Database Management Systems. At the end of each chapter, summary is given to
quickly recap the concepts. The exercises include theory questions, multiple-choice questions,
andquestionsforstudent’spractice.Theoverviewofemergingtrendsindatabasesisthoroughly
explained. This book addresses the need of B.Tech, M.C.A., and IT programme students, faculty
members, and professional developers. I am sure that they will be benefited from this book.
Shefali Naik, the author of this book, is working as senior faculty member, since past thirteen
years, at the School of Computer Studies of the Ahmedabad University. She teaches courses
on database management systems at graduate and post-graduate levels. To her credit, she has
written a good number of articles and technical papers in the area of databases. I wish her good
luck for authoring this book and her academic career.
—Bipin V. Mehta
Director
School of Computer Studies,
Ahmedabad University
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Preface
This is the first edition of this book. I have tried to cover all the concepts of database manage-
ment system. This book is useful for the students of computer science, IT, and the courses in
which database is offered as an interdisciplinary subject.
The readers who are new to this subject, can start this book reading from the first chapter.
Those who are already familiar with databases, can read any chapter to know more about it.
Readers, who are willing to learn about any Relational Database Management System, may read
Chapters 11 and 12 which gives brief details on MS-Access and Oracle RDBMS, respectively.
Readers, who are interested in advancement in database, may read Chapters 8, 9 and 10 which
describe advanced topics in database, such as Transactions, Distributed Database, and emerging
trends in Database. Those who wish to learn programming language used in database, may read
Chapters 6 and 7 in which SQL and PL/SQL is discussed.
The details covered in each chapter of this book are as follows:
●
● Chapter 1 gives an overview of database by explaining the basic concepts of database,
such as data, information; database management system’s advantages on other record-
keeping system and limitations, its components, etc.
●
● Chapter 2 describes the evolution of database management system from different sys-
tems, such as hierarchical model and network model. It also describes the architecture of
DBMS.
●
● Chapter 3 explains Relational Database Management System.
●
● Chapter 4 explains Entity-Relationship Model, and Chapter 5 describes Normalization
Process.
●
● Chapters 6 and 7 explains the common languages SQL and PL/SQL, which is used in
relational database systems to create and manage database objects; add, remove, change
and retrieve data to/from tables and write small programs.
●
● In Chapter 8, Transaction is discussed; Chapter 9 explains Centralized and Distributed
database, and Chapter 10 describes advancement in databases.
●
● Chapters 11 and 12 cover two well-known relational database management systems MS-
Access and Oracle.
Any suggestions to improve the content of the book are welcome.
—Shefali Naik
FM_Final.indd 9 3/18/2014 5:02:47 PM

Acknowledgements
I am indebted to many people who were directly or indirectly involved with the creation of
this book.
I would like to thank Bipin V. Mehta, Director at the School of Computer Studies of the
Ahmedabad University, for his inspiration and contribution with the Foreword of this book.
I am grateful to my colleague and friend, Pratik Thanawala, for his technical suggestions
which helped me to improve the contents of this book. I am thankful to my friends from other
universities, Sonal Jain, Shivani Trivedi and Tripti Dodiya, for their guidance.
I would like to acknowledge the assistance provided by the editorial team of Pearson
Education, Noida; especially, Neha Goomer and Nikhil Rakshit, for their continuous assistance
in solving various queries related to the publishing of this book. I am also thankful to Uma
Tamang and Naresh Sharma. A big thanks to Pearson Education for publishing this book.
I thank my parents, Girish and Bharati Naik, and children, Jisha and Harsheev along with
rest of the family, for their love and patience. Finally, I owe it to my husband Trushit, for his
constant support and encouragement.
—Shefali Naik
FM_Final.indd 11 3/18/2014 5:02:47 PM

About the Author
Mrs Shefali Naik, the author of this book, is working as a senior faculty member for past 13 years
at School of Computer Studies, Ahmedabad University, Ahmedabad. She teaches subjects related
to Databases, Programming, Systems Analysis and Design, and Software Project Management
at undergraduate and post-graduate levels. She has obtained her Master’s degree in Computer
Applications (M.C.A.) and Bachelor’s degree in science with mathematics as a special subject
(B.Sc., Mathematics) from Ahmedabad, Gujarat.
The author has written few technical papers and articles in the area of databases.
Presently, she is pursuing her Ph.D. from S.P. University,VallabhVidyanagar,Anand, Gujarat,
in the subject of Distributed Databases.
FM_Final.indd 13 3/18/2014 5:02:48 PM

CHAPTER
1.1 | Introduction
In the current era, people of all ages use database in one way or the other. Everyone uses
database in different ways. For example, school children use database of e-mail programs and
mobile phones, youngsters use online movie and railway ticket booking database to book tick-
ets, housewives use database of books to order books online or access various community site’s
database, businessmen use database of airlines to book their trips, academicians use online
journals database to do research work and many more. Nowadays, computers are used every-
where. We may reform the proverb ‘Where there is a will, there is a way!’ as ‘Where there
is a computer, there is a database.’ Computerized Databases have made our life very easy and
comfortable. We can search any place, product, area, thing, etc., with the help of stored data in
a fraction of a second. Stored data processed with the help of database management systems
extracts the desired information, every time. Let us understand the database in some more detail.
1.2 | Data and Information
1.2.1 | Data
Data is a plural of word ‘datum’. In our daily life, we use the word data to describe facts about
any person, event, place or thing. Data are raw facts which may be numbers, values, names,
1
Basics of Database
• Understanding the meaning of data and information.
• Knowing how database and database management systems are useful in organizations to keep
records.
• Examples of database management system.
• Components of database system.
• Characteristics of data and DBMS.
• Differences between file-based management systems.
• Limitations of DBMS.
Chapter Objectives
CH_1_Basics of Database_Final.indd 1 2/26/2014 3:36:03 PM

2 | Chapter 1
dates, etc. When we combine related data, they describe any real-world entity. Related data
means data which belong to the same entity (person, place, event or thing). For example, If
we consider the entity ‘Doctor’ (person type of entity), then doctor’s name, doctor’s address,
doctor’s birth date, doctor’s qualification, doctor’s specialization, etc., are data related to
doctor. We cannot say that supplier’s name and doctor’s qualification are related data;
because both describe two different entities named supplier and doctor. Thus, when we want
to describe any real-world entity, we use data values. Data values alone do not have any
meaning because they are not processed yet.
1.2.2 | Information
When we process related data it gives some information. Information is useful to take deci-
sions, it can be stored for future use, it has some meaning. To obtain information, we need data.
For example, when we process students’ attendance data, we can get a list of students with low
attendance, students who are attending lectures regularly, students who come to college to at-
tend particular lectures, pattern of class bunking for each student, etc.
On the basis of this information, the college may decide the attendance policy, reschedule
the time-table to improve attendance, decide whether to inform parents or not, determine which
students should be allowed to sit for an examination, etc. This information could also be stored
for future use. In case, when students need a transcript, this information can be used to fill up
lecture-wise attendance details of each student or to generate attendance certificates which may
be required along with migration certificates when students change universities.
Data can be stored manually or electronically. Similarly, stored data may be processed manu-
ally or electronically. Table 1.1 shows some examples of data and information.
We can show the relationship between data and information as given in Figure 1.1.
Figure 1.2 shows an example of data and information.
Table 1.1 shows some examples of data, processes which should be applied on stored data
and information which could be obtained after processing certain data.
Table 1.2 shows a student’s examination result data which can be processed as per the follow-
ing condition to obtain grade-wise Result analysis.
Table 1.1 | Examples of Data and Information
Data Process Description Information
Census data Sort records based on area and count
total no. of persons gender-wise and
age group-wise
Area-wise male and female
ratio for different age groups
Board Exam Data Count subject-wise, no. of students
who passed or failed in an exam
Subject-wise total no. of passed
or failed students
Climate Data Maximum temperature and minimum
temperature during the year
Hottest and coldest day of the
year

Basics of Database | 3
If percentage 40 then, Grade = ‘F’
If percentage ≥ 40 and 50 then, Grade = ‘D’
If percentage ≥ 50 and 60 then, Grade = ‘C’
If percentage ≥ 60 and 70 then, Grade = ‘B’
If percentage ≥ 70 then, Grade = ‘A’
The following sample information may be obtained after processing the data given in Table 1.2:
Class-wise Result Analysis
Table 1.2 | Students’ Examination Result Data
Std No. Class Code Std Name Percentage Gender
1 FY Mitali Gupta 89 Female
2 FY Nirav Valera 91 Male
3 FY Jainam Vora 79 Male
4 FY Rajani Vyas 57 Female
5 FY Nidhi Jain 64 Female
1 SY Kartik Bhatt 82 Male
2 SY Kanika Yadav 84 Female
3 SY Karishma Yadav 70 Female
4 SY Siddharth Soni 39 Male
5 SY Akash Patel 69 Male
1 TY Paras Sanghvi 84 Male
2 TY Pankti Bindal 94 Female
3 TY Richa Singh 75 Female
4 TY Neel Shah 59 Male
5 TY Payal Shah 60 Female
Process
Data Information
Figure 1.1 | Relationship between data and information.
Students’ Attendance Data
Percentage of lectures attended by student
Total no. of lectures attended × 100
Total no. of lectures conducted
Data
Process
Information
Figure 1.2 | Example of data and information.

4 | Chapter 1
Class code: FY
No. of students who got ‘A’ Grade: 3
No. of students who got ‘B’ Grade: 1
No. of students who got ‘C’ Grade: 1
No. of students who got ‘D’ Grade: 0
No. of students who got ‘F’ Grade: 0
Class code: SY
Class code: TY
Overall total no. of students who passed in the exam:14
Overall total no. of students who failed in the exam:1
The above information may be stored and processed further to represent the result analysis
graphically or pictorially using bar charts as represented in Figure 1.3. X-axis will contains
class code and grades, and Y-axis contains total number of students.
1 1 1 1
1 1
0 0 0 0 0 0
FY
3
2.5
1.5
0.5
0
1
2
SY TY
3
3
3
A
B
C
D
E
Figure 1.3 | Bar chart represents class-wise grade-wise total number of students.

1.3 | database
As the name suggests, database is a collection of data, i.e., database is a storage area where we
can store all related data and process them. To understand the concept of database, let us take
some real-time examples of database (storage). One logical database which we carry with us
all the time is our brain. The brain stores all thoughts, ideas and things which we learn, view,
etc. and it relates them. We can retrieve, change or remove these stored ideas and thoughts any
time. The example of real-time physical database is a grain warehouse. When it is the season
for some grain/pulses, we store them and use them later as per the process requirements. When
we process the grains/pulses we obtain the information in the form of floor, sprouts, etc., which
could be used in further processing to cook food. The pulses/grains which we find useless could
be removed from the warehouse and could be replaced (updated) with fresh stock. In real-life,
we use the concepts of data, information and database everywhere.
Figure 1.4 shows an example of real-life database of children’s’ schoolbag. It is a stationery
database which contains entities such as notebook, textbook, compass box, geometry case, etc.
Entity Notebook has distinguished notebooks of various subjects; Entity Textbook has distin-
guished textbooks of various subjects; Entity Compass box has pencils, erasers, sharpeners,
ruler, etc., and Entity Geometry box has common mathematical tools.
A database is like an electronic storage, which contains computerized data files (entities).
It can contain one or many data
files. Data files contain various
related data within it. Database
should contain accurate, con-
sistent and non-redundant data
which could be shared by differ-
ent application programs. Data
can be related by defining rela-
tionships between proper data.
Also, conditions (constraints)
may be applied on data. Different
users may access different data
sets from the same database by
writing application program. We
may put security and authentica-
tion procedures to provide autho-
rised access of data. There may be
more than one database within a
database management system. All
related entities are kept together
in the same database. Data within database can be retrieved, updated or deleted directly by
database administrator or by authorized users or application programs written by users. To
describe data, other details are stored along with the data such as data type, size, constraints,
description, format, etc. Using this information, the database management software generates
data dictionary which contains ‘data about data’ or ‘metadata’.
Schoolbag: A database
of stationery items
Notebook: An entity
within a database
Geometry box: An
entity within a database
Compass box: An
entity within a database
Textbook: An
entity within a
database
Geometry box: An
fIGure 1.4 | Real-life example of a database.

6 | Chapter 1
Database contains data stored in computer. To process the stored data, we need application
programs. The processed data could be again stored into database for future use. The data, on
which we can do some processing, is known as operational data. Any organization contains
operational data. Table 1.3 contains some examples of organizations and operational data of a
particular organization.
A database stores data of various entities. These entities can be related using relationships.
Data also contains description, which is known as metadata. Along with the data, one can keep
constraints on its data types.
A cylindrical shape, as shown in Figure 1.5, is used to represent physical database. Physical
database is useful for the computer (i.e., how a machine sees data), while logical database is
useful for the user (i.e., how a human being sees data). It is a database of a university, which
contains various related entities, such as course, college, student, class, attendance, exam, etc.
There are many colleges in a university; each college contains many students in different courses
and classes. Students attend lectures, appear in exams and get results.
The ‘University’ database contains interrelated data which could be shared by different ap-
plication programs to obtain meaningful information.
1.3.1 | Components of Database System
Figure 1.6 shows components of any conventional database system.
1. User: User is any person who uses a database or any other object of the database. User
may be of different types and at different levels in an organization. Say for example, the
‘University’ database may be useful for different persons who are directly or indirectly as-
sociated with the university. Following are some categories of users who may use database.
Figure 1.5 | Example of ‘University’ database.
College
Attendance Class
Exam
Student
Course
Table 1.3 | List of Some Organizations and Related Operational Data
Organization Operational Data
Public Library Member data, Books data, Publisher data, etc.
Restaurant Customer data, Employee data, Food Items data, etc.
Super Mall Product data, Customer data, Supplier data, etc.
University Student data, Faculty data, Exam data, etc.
Hospital Patient data, Doctor data, etc.

a. Naive User, or End-user, or Layman: The clerk of the university uses the ‘university’
database to enter the data of applicants who have applied for various courses and the
same data are retrieved to generate a merit list. The clerk does not know anything about
the technical features of the database or the language, using which data is entered or
retrieved. He is completely unaware about the technology. Therefore, he/she is known as
an end-user or Layman or Naive user. Table 1.4 shows some examples of databases and
end-users of that database.
b. Software Programmer, or Application Programmer, or Application Developer: A soft-
ware programmer is a person who writes application programs or logic in some specific
language to insert, delete, update or fetch data to/from database. An application program-
mer has brief knowledge about database and Query Language which is used for writing
programs. Query Language is a generalized language which is available with all data-
bases. A programmer may or may not have deep understanding about database concepts,
but he/she is able to operate on data stored in the database.
Table 1.4 | Examples of End-users
Database End-user
Online University Database Applicants, Parents, University Staff, etc.
Hotel database Customer, hotel Employees, etc.
Online Railway Reservation
Database
Citizens of the country, Agents, Railway
officials, etc.
Figure 1.6 | Components of database system.
Datafile 1 Datafile 2
Data 1
Data 1
Data 2
Data 2
Data 2
D
a
t
a
f
i
l
e
1
D
a
t
a
f
i
l
e
2
Data2
D
a
t
a
2
D
a
t
a
f
i
l
e
2
D
a
t
a
1
D
a
t
a
2
D
a
t
a
1
User(Software
programmer)
writes programs
to view data
User(DBA) writes
validation programs
and manages
security on
Hardware on which
database is stored
Programs
programs
programs
Programs
programs
programs
Programs
Programs
Datafile 2

8 | Chapter 1
c. Database Designer: A database designer decides about entities (data files) which should
be stored within database, constraints to be applied on data, data types, format and
other specifications regarding data. The database designer is responsible for designing
of data files.
d. Database Administrator: A database administrator (DBA) is the person who is the over-
all in-charge of a database. He/she assigns authorization to users, writes validation proce-
dures, decides backup and recovery policies, and manages users and privileges. In short,
DBA keeps control on database.
2. Hardware: Hardware is a permanent storage where the database is stored. It may be a
hard-disc, or any other secondary memory. One single database may be stored on more
than one storage devices depending on the volume of data stored within the database. For
security purpose, a copy of database could be kept on some other storage device. Besides
storage device, other hardware, such as computer, peripherals, etc., are also required to
perform database-oriented operations.
3. Software (data dictionary management, database schema management, SQL):
Software are programs or applications which are used to access data from database.
These applications reside in DBMS or there may be some applications which could be
interfaced with DBMS to manage data. For example, programming languages are used
to display data on monitor. There are some software programs, which are part of DBMS,
that manage data dictionary or metadata, define schema for the database objects, and are
used to write query on database. The common language available with all the databases
is known as Structured Query Language; if which is popularly known as SQL and
sometimes pronounced as ‘Sequel’.
4. Data: Data is the most important component of a database system. Data is discussed in
detail in Section 1.1. When data is stored in database, it should be stored along with its
definition, data type and size, constraints, such as duplicate values are allowed or not,
possible range of values, formula if it is derived from some other data, etc., display format,
format in which it should be entered, validation rules, etc. Some examples of data
files/entities (tables) and data stored within the entity are given in Tables 1.5, 1.6 and 1.7.
These data files are inter-related data files which are part of the playschool’s database.
Table 1.5 | Example of Data within Data File ‘Kindergarten’
Data Name Data Type (Size) Constraint Input Format Display Format
Data File Name: Kindergarten
KG id Integer Unique number which
Should be generated
automatically.
— —
KG name Character(30) Must be entered. Should be entered
in upper case.
Should be dis-
played in title
case.
Address Character(100) — — —
No. of branches Integer ≥0 — —
Contact no. Integer — — —
Contact person Character (20) — — —

Table 1.6 | Example of Data within Data File ‘Class’
Data File Name: Class
Class code Character (3) Must be entered Should be entered
in upper case.
Should be displayed
in upper case.
Class desc. Character (30) — — —
Class capacity Integer 0 and ≤30 — —
No. of divisions Integer 0 and ≤4 — —
Age criteria Float ≥2 — —
Table 1.7 | Example of Data within Data File ‘Class’
Data File Name: Kindergarten Detail
Class code Character(3) Must be entered Should be entered
in upper case.
Should be displayed
in upper case.
KG id Integer Must be entered — —
Division Character(1) Upper case — —
No. of students Integer 0 and ≤30 — —
Table 1.8 | Example of Data Values within Data File ‘Kindergarten’
KG ID KG Name Address No. of Branches Contact No. Contact Person
Data File Name: Kindergarten
1 Innocent
Flower
Naranpura,
Ahmedabad
1 27417411 Mr S. T. Pandya
2 Smart Kids Navrangpura,
Ahmedabad
3 27477471 Ms K. P. Verma
3 Kids Zone Satellite,
Ahmedabad
4 26306301 Mr A. R. Nair
4 Teacher’s Pet Naranpura,
Ahmedabad
2 27567561 Mr T. R. Khanna
5 Little Star Ambawadi,
Ahmedabad
1 26466461 Ms N. J. Gupta
When data are entered into tables, Kindergarten, Class and Kindergarten Details (Tables 1.5,
1.6 and 1.7 respectively); the correctness of data are checked. Invalid data cannot be entered
into data files.
Tables 1.8, 1.9 and 1.10 contain some valid data values for the tables Kindergarten, Class and
Kindergarten Details, respectively.

10 | Chapter 1
Table 1.9 | Example of Data Values within Data File ‘Class’
The data in a database must have the following characteristics:
●
● Same data should be shared between different applications. For example, if there are two
departments , namely ‘accounts’ and ‘examination’, in a university, then data related to
student should be shared by these two departments. There should be no need to create a
copy of the same data.
●
● When data are shared, there is a question of integration. Integration means, changes in
one data file should also be reflected in the related data file. For example, if a clerk in the
accounts department deletes a record of any student, then it should also be deleted from
‘member data file’ used by the ‘library’ department of that university.
●
● When data are properly integrated, there are minimum chances of inconsistent data.
Data will be consistent if they are integrated properly.
●
● Data should be non-redundant: If possible to avoid duplication of data in different files,
data should be stored in one file, and whenever required, it should be referenced from the
original file. It is not possible to remove redundancy at all, but we should try to avoid redun-
dancy. Redundant data causes inconsistency within a database. For example, if a student’s
address is stored in the ‘enrolment’ file as well as in the ‘alumni’ file, then ‘address’ entry
for the same student would be redundant. Now, when the student’s address is changed,
the clerk changes the ‘address value’ in the ‘student’ file. He forgets to change address in
Class Code KG ID Division No. of Students Class Code KG ID Division No. of Students
Data File Name: Kindergarten Detail Data File Name: Kindergarten Detail
PG 1 1 15 JRKG 2 1 30
PG 1 2 13 JRKG 2 2 30
NUR 1 1 25 JRKG 2 3 30
NUR 1 2 25 JRKG 2 4 30
NUR 1 3 25 SRKG 2 1 30
NUR 1 4 25 SRKG 2 2 30
JRKG 1 1 30 PG 3 1 14
JRKG 1 2 30 PG 3 2 14
JRKG 1 3 30 NUR 3 1 20
JRKG 1 4 30 NUR 3 2 20
SRKG 1 1 30 NUR 3 3 20
SRKG 1 2 30 NUR 3 4 20
PG 2 1 15 JRKG 3 1 30
PG 2 2 10 JRKG 3 2 30
NUR 2 1 25 JRKG 3 3 30
NUR 2 2 25 JRKG 3 4 30
NUR 2 3 25 SRKG 3 1 20
NUR 2 4 25 SRKG 3 2 20

Table 1.10 | Example of Data Values within Data File ‘Class’
Class Code Class Describe Class Capacity No. of Divisions Age Criteria
Data File Name: Class
PG Play Group 20 2 2
NUR Nursery 25 4 2.5
JRK Junior KG 30 4 3.5
SRK Senior KG 30 4 4.5
the ‘alumni’ file. So, now database will show different addresses for the same table which
is conflicting. This is called ‘data inconsistency’, which occurs due to redundant data.
●
● Data should represent complete details. For example, only customer’s first name entered
in the name field represents incomplete detail. It should contain at least first name of the
customer along with the surname.
1.4 | Database Management
The process of managing data within database is called database management. To manage
database, a database management software/system is required. Database management includes
the following activities:
●
● Writing schema for creating new data files, updating structure of existing data file, delet-
ing a data file.
●
● Setting relationship among data files.
●
● Inserting, deleting and updating data values within data files.
●
● Maintaining data dictionary.
●
● Creating, updating and deleting database objects other than data files, such as views,
synonyms, procedures, functions, triggers, indexes, etc.
1.5 | Database Management System
Database management system is a collection of application programs which is used to man-
age database objects. Database Management System is a generalised software which is used to
manage database and database objects, such as tables, users, procedures, functions, etc., and
to connect database with any front-end (language) with the help of some hardware. Many types
of database management systems are available in the market nowadays. One can purchase
license of any database from its vendor and start using it. Also, there are some open source
database management systems for which there is no license required to use it. It is available
on the Internet. One can download it and use it. The source code is also available for free which
could be modified by any user and redistributed. MySQL is one of the most popular open source
database management system. Table 1.11 contains some examples of database management
system and the vendor company who provides it.

12 | Chapter 1
1.6 | Need for A Database
Following are some reasons for the need of a database:
●
● Database is required for efficient and easy storage, retrieval, updation and deletion of data
records.
●
● Interrelated data should be grouped in one named storage area for easy access. This storage
area may be physical or logical which resides in computer.
●
● For avoiding unnecessary repetition of data values, checking correctness of data by applying
some validation rule, and searching the required information faster thus saving time and ef-
fort, etc.
●
● Database is required for flexibility, i.e., as and when required we can connect the database
with different front-ends.
●
● Once a database is created, it can be shared by many users. Hence, to share data with many
applications a database is required.
●
● Database is needed for storing high volume and complex data, such as documents files, pho-
tographs or images, multimedia data, mobile user’s data, audio and video files.
●
● For managing multi-dimensional data.
●
● Database is required for proper transaction management or transaction handling.
1.7 | File-based Data Management System
File-based data management system is used by programmers to manage data. Languages, such as
C or COBOL contain file management system within it. Figure 1.7 shows a file-based system for
any ‘Playgroup’ in which different data files are used to manage admissions in (a) Nursery, (b)
Junior KG and (c) Senior KG—for which different application programs should be written to
handle different procedures. In file-based systems, data are managed using data files and these
files are created and manipulated by writing application programs. Each application program
contains its own data files.
File-based management system has the following disadvantages:
●
● File-based management system is not appropriate when volume of data is very high.
For example, it will be difficult to handle when daily transactions are in thousands
or more numbers.
●
● When number of data files increase, it becomes very complicated to manage data files,
i.e., if number of data files increase, number of application programs are also increased;
because to insert, update, delete or view data to/from data files, an independent applica-
tion program is to be written.
Table 1.11 | Examples of DBMS and Its Vendors
Database Management System Vendor (Supplier)
Oracle Oracle
SQL Server Microsoft
Access Microsoft
DB2 IBM

●
● Complex data structures, such as pointers, cannot be handled easily by a file-based
system.
●
● When the same data file is required by different programs at the same time, data sharing
is not possible. To use same files at the same time, copy of that data file must be created
and used. When these are two or more copies of same data file, it may result in inconsis-
tent and redundant data, because changes made in one file may not be carried out in the
other files.
●
● In a file-based system, the programs should only be written in a structured manner.
●
● It is not possible to set relationships between data files. Programs should be written to
relate them.
●
● Security settings cannot be applied on data files.
●
● Set of data files created in a specific file-based system cannot be used with other file-
based systems as storage formats of different file-based systems vary.
Database system is required to overcome the limitations of file-based management system. The
traditional database system contains data files which could be used to store data. The examples
of simple database management system are dBASE and FoxPro. These DBMS contains CUI
(Character-based User Interface) which provides faster access of data using commands. There
is no need to create data files manually. In simple DBMS, data files with data field names and its
data type can be created. However, a simple DBMS does not provide the facility to define keys.
Student
datafile
Applicant
datafile
Enrolment
process
Class
datafile

Attendance
datafile
Class
datafile
Student
datafile
Attendance
process
Result
process
Result
datafile
Exam
datafile
Student
datafile
Class
datafile
Figure 1.7 | File-based management system to manage data of ‘Playgroup’.

14 | Chapter 1
As keys cannot be defined, it is not possible to define relationship between data files either. If
user wants to relate data files, then he/she has to write programs to relate two or more file. An
example of such a program is given below in Figure 1.8.
But the advantage of simple DBMS, over file-based system, is that we can share data files be-
tween applications. Simple commands can be used to search, insert, update, delete and view data.
1.8 | Characteristics, or Features, or Advantages
of Database systems
●
● It provides facility to use same data file with different applications, i.e., data can be shared.
As shown in Figure 1.8, ‘Employee’ data file can be used by ‘Accounts’ department to
generate salary slip and by ‘Human-Resource’ department to evaluate the performance
of the employee.
●
● Duplication of data can be minimized. There is no need to enter same data again and
again as data can be shared between different applications.
●
● Proper transaction management is provided by DBMS. When data are shared between
applications, there is a problem of updation when two users try to change same data at
the same time. Data can be changed by only one user at a time. DBMS itself decides the
priority to allow only one user to change the data at a time. The priority is decided by the
DBMS software on the basis of some algorithms. In this way, DBMS handles transac-
tions more efficiently than the file-based management system.
●
● There is no need to write long programs to manage data. It can be done by writing a
simple single line command using structured query language, which is the generalized
language provided with DBMS software.
●
● It is easy to maintain data file structures in DBMS using structured query language.
●
● Data can be integrated easily, i.e., change in one data is reflected automatically in the
related data file’s data. For example, if we delete any record from ‘Customer’ table, the
related child records from ‘Purchase Order’ data file will be deleted.
●
● Data inconsistency can be avoided. As data are integrated, user is not bothered about up-
dation of same data in different data files. It is handled by the database software. In this
way, data will be consistent.
●
● User management becomes easier. There may be many users of the same database who
may access the database from local or remote machines. By providing user rights and
authorization checks, the DBMS can control and restrict users.
Accounts
department
Human-resource
department
Employee
data ﬁle
Figure 1.8 | Example of data file of DBMS which is shared by various departments in an
Organization.

Table 1.12 | File-based Management System vs. Database Management System
File-based Management System Database Management System
Needs individual application program to per-
form any operation on data file.
Any operation on data file is done using
single-line commands.
Programming is done using 3GL (Third Genera-
tion Languages, such as COBOL, C, PASCAL).
Programming is done using 4GL (Fourth
Generation Languages such, as SQL-
Structured Query Language).
Transaction management is very difficult. Transaction management is easy.
Same data file cannot be used simultaneously. Same data file can be used simultaneously.
Security features cannot be enforced. Security features can be enforced.
Backup and recovery facility is not available. Backup and recovery facility is available.
Duplication of data cannot be minimized. Duplication of data can be minimized.
Examples: C, COBOL, PASCAL languages’ file
management system.
Example: dBASE, FoxPro, MS Access, Oracle.
●
● Validation rules can be applied on data before data is entered in the database. It will pre-
vent wrong data inputs.
●
● Change in data file structure becomes very easy.
●
● Security can be enforced on data by assigning privileges for different users.
●
● Appropriate backup procedure is available to avoid loss of data in any adverse circum-
stances, such as power failure, server failure, hardware crash. In case of failure, the data
can be recovered using recovery procedures.
●
● DBMS provides Import and Export facility using which data files can be imported from
one DBMS and exported to another.
Table 1.12 shows the difference between file-based management system and database manage-
ment system.
1.9 | Limitations of Database
Nothing is 100% perfect. Advantages also bring along limitations with them. Database manage-
ment system also has some limitations. They can be described as:
●
● Cost of database management system is very high. As the number of users increase, we
need to pay more.
●
● To install database in a network, high-end hardware and skilled personnel to manage the
network and database is required.
●
● As data can be shared through DBMS, it is difficult to control and keep track of data ac-
cessed by users. Proper encryption and decryption techniques are required to secure data
over a network.
●
● Efficient employees are required to handle users and decide policies about data access,
which requires considerable and constant training.

16 | Chapter 1
●
● If data volume is very high, performance will be poor. Also, when too many users are
using database at the same time, it may generate traffic on network and slow down the
response time.
●
● It will be more complex when DBMS contains many databases within it. It may reduce
the speed of data access.
Summary
●
● Data means raw facts. It may be any values, such as integer numbers, float numbers,
characters, dates, images, Boolean.
●
● Examples of integer type of data are roll numbers form number, order number; float type
of data are salary, balance amount, fees, product price; character type of data are person’s
name, address, qualification, product name; date type of data are birth date, admission
date; retirement date, order date; image type of data are person’s photo, image of property
location, image of property; Boolean type of data are customer status, payment status,
gender.
●
● Interrelated data represent any entity, i.e., data are characteristics of entity. For example,
student name, student birth date and student gender are data (characteristics) related to
student entity. An entity is a distinguishable object of real-world.
●
● Data related to an entity are kept together in a data file, i.e., data file is a collection of
related data.
●
● Data may be stored manually or electronically. When we apply any process on stored
data, it gives some valuable information. The process on data stored electronically can be
applied by writing application programs.
●
● The data on which we do some operation, is known as operational data. Operational
data belongs to any organization. For example, student’s data is an operational data for
the ‘University’ organization. By processing student’s data, we can generate information
like a student’s mark sheet, list of college-wise total number of students, etc.
●
● Database is a collection of data files or tables which contain data within it. Relationship
can be set to access data from different files.
●
● The process of managing data within database is called database management.
●
● Database system contains the components data, user, hardware and software.
●
● Using database we can share and integrate data between applications.
●
● Database management system is a collection of software programs through which
database can be managed.
●
● File-based management system requires manual creation of data files which are very dif-
ficult to handle. Within file-based management system, independent programs should be
written to do operations such as insert, delete, update and view data.
●
● Database management system provides structured query language to store and access data
from database. There is no need to write long programs to access data. Data redundancy
and data inconsistency problems can be avoided using database management system.

●
● Database management system provides automatic transaction management, backup and
recovery facility, export and import facility, user management and other functionalities.
●
● The limitations of database management systems are: they are complex, expensive,
requires knowledge to use them, data control is difficult, performance may suffer because
of high data volume, etc.
Exercises
1. Define Data and Information. Show relationship between these two.
2. Give any two examples of data. Write any two types of information which could be ob-
tained by processing these data.
3. Define the terms:
a. Database
b. Database management
c. Database management system
d. Operational data
e. Metadata
4. For any restaurant system, which data are operational data? Write two examples of infor-
mation related to that.
5. Draw a diagram of components of database system and explain.
6. List down different types of users of database system with their roles.
7. Name any four DBMS along with their supplier company.
8. What is an open source database? Give an example.
9. Which are the characteristics or features of data in a database?
10. Write a short note on file-based management system.
11. Give an example of file-based management system. Mention the disadvantages of this
system.
12. List down and explain advantages of database management system over file-based man-
agement system.
13. What are the limitations of database management system?
14. Discuss data redundancy and data inconsistency with relevant example.
15. Write/Tick the correct answer.
i. Data means:
a. Unprocessed facts b. Processed facts
c. Unprocessed information d. Processed information
ii. The operational data related with ‘Hostel’ are:

a. Mess data b. Customer data

c. Patient data d. Doctor data
iii. DBMS is an abbreviation of ______________.
a. Database Management System b. Distributed Management System
c. Data Management System d. Database Modification System

18 | Chapter 1
iv. Database contains data files or tables.

a. True b. False
v. Data represents ______________ of an entity.
a. Relationship b. Definition

c. Type d. Characteristics
vi. DBMS supports structured query language (SQL) which is _________.

a. 1GL b. 2GL

c. 3GL d. 4GL
vii. The user who does not know working of a database is called _____________.

a. End-user b. Database Designer

c. DBA d. System Analyst
viii. _____________ is responsible for overall control of database.
a. Data Analyst b. Database Administrator
c. Programmer d. End-user
ix. Among the following, which one is not a component of database system?

a. Hardware b. Data

c. Software d. None
x. Data redundancy causes ________________ data in database.

a. Accurate b. Complete

c. Meaningful d. Duplicate

CHAPTER
2
Data Models and Architecture
of DBMS
• Evolution of data models.
• Knowing the traditional data models.
• Advantages and disadvantages of various types of data models.
• Three-level architecture of database management system.
• Understanding languages used to define objects, manage and control data and transaction.
Chapter Objectives
2.1 | Evolution of Data Models
●
● Data are the primary requirement of any application. It is important to store data appropri-
ately for easy access. During the 1940s and 1950s, use of computer to write applications
in programming language for automation increased. The file-based management system
was not sufficient to manage data. Hence, evolution of data models took place. Figure 2.1
shows the block diagram of evolution of data models from manual record keeping system
to file-based management system, and from file-based management system to database
management system.
●
● COBOL (Common Business-oriented Language) and FORTRAN (Formula Translation)
were two primary programming languages used to create enterprise applications during
the 1950s. The file systems of these languages were not able to handle data which are
required by the applications developed in these languages.
●
● Therefore, in the 1960s, IBM and Rockwell International developed a hierarchical data-
base system named IMS (Information Management System). Later, C.W. Bachman pro-
posed Network Data Model and, on the basis of this model, General Electric developed
a network database model named IDS (Integrated Data Store). Both IMS and IDS were
accessible from the programming languages using an interface. Using these database
systems, application development and data management within application had become
easy, but a complex task.
CH_2_Data Models and Architecture of DBMS_Final.indd 19 2/26/2014 3:37:02 PM

20 | Chapter 2
Manual record keeping
Data kept manually
.
.
.
Data stored in computerized
ﬁle using ﬁle-based management
system
Data stored in database using
database management system
Figure 2.1 | Evolution from manual record keeping system to file-based management
system and, from file-based management system to database management system.
●
● In 1970, Edgar F. Codd proposed a different data model, in which he had suggested that
data in a database could be represented as a two-dimensional table structure, which is
known as relation, and could be accessed without writing lengthy programs to access
data. This model is known as relational data model. Nowadays, many vendors provide
relational database management systems. Some well-known RDBMS are MS-Access and
MS-SQL Server provided by Microsoft; Oracle provided by Oracle; DB2 provided by
IBM, and many more.
●
● Along with RDBMS, the object-oriented concept evolved. The use of object-oriented
programming languages increased in the 1980s, and along with it increased the need
of a database system which would be able to handle classes and objects. Thus, evolved
the object-oriented data model. Many vendors had developed OODBMSs namely Gem-
Stone, ObjectDesign, Versant, O2, Objectivity, etc.
●
● Extensive use of object-oriented languages resulted in an object-relational DBMS
which is a combination of object-oriented and relational DBMS. Many vendors, such as
Oracle, IBM, provided functionalities of object-oriented concepts in their RDBMS (see
Figure 2.2).

Data Models and Architecture of DBMS | 21
Data Models
Hierarchical
Example: IMS,
Mark IV
Network
Example: IDS, DMS
1100
Relational
Example: QBE,
MAGNUM,
Oracle
Object-oriented Object-relational
Example: OPAL Example: Oracle
Figure 2.2 | Data models.
2.2 | Hierarchical Data Model
●
● The data model describes data and its definition. In case of an object-oriented data model,
it describes the object and its behaviour. A data model is a logic which is based on con-
cepts, while its implementation is called, ‘database management system’, i.e., database
management system is a physical implementation of data model. Entity-relationship
model is a conceptual model which shows entities and relationships between entities.
●
● The hierarchical data model was the very first data model developed in the 1960s. The
hierarchical data model named IMS (Information Management System) was developed
by IBM and Rockwell Company and widely used during the 1960s and1970s. The enti-
ties and relationships between entities were managed with the help of a tree-like structure
in the hierarchical model. In this tree, there exists a root and it is related with its child. A
root is known as a parent. One parent may have many children in hierarchical structure,
but one child cannot have more than one parent, i.e., if there is a child entity which is
related with more than one parent entities, then two independent parent nodes should be
created which contains redundant child records. The redundant child records should be
linked with both the parents. On root, there will be entity occurrences from the parent
entity. One entity occurrence means one segment. If this segment is on the root, it is
called root segment. The entity occurrence, which falls under the root segment (parent),
is known as dependent segment (child), i.e., collection of entity occurrences are called,
‘segments’. Root segment and dependent segments are connected through link. In a
hierarchical structure, one root segment may have many dependent segments, but a de-
pendent segment will have only one root segment. To explain this, many-to-many rela-
tionship between root and dependent segments is not possible in a hierarchical structure.
●
● Entity occurrence from parent entity is shown as a root segment, and its related entity
occurrences are shown as its dependent segments. The entity occurrences of same entities
are shown at the same level in a tree. The related entity occurrences, which fall under it,
are its branch.
●
● To give an example, consider the entities given in Figures 2.3 and 2.4. Figure 2.3 contains
entities Zone, Region, Item and Area; while Figure 2.4 contains entities as Salesman and
Sales. All the entities are related with the following relationships with each other.

22 | Chapter 2
●
● Figures 2.3 and 2.4 represents the following entities:
○
○ Zone
○
○ Region
○
○ Area
○
○ Item
○
○ Salesman
○
○ Sales
Region
Region ID Region Name Zone ID
1 Punjab 1
2 Himachal Pradesh 1
3 Gujarat 4
4 Maharashtra 4
5 West Bengal 2
6 Kerala 3
7 Karnataka 3
8 Andhra Pradesh 3
9 Rajasthan 4
10 Bihar 2
11 Assam 2
13 Jammu and Kashmir 1
Zone
Zone ID Zone Name
1 North
2 East
3 South
4 West
Item
Item No Item Desc. Price (in `)
1 Bulldozer 200000
2 Soil Stabilizer 300000
3 Scraper 350000
4 Excavator 200000
5 Dump Truck 150000
Area
Area Code Area Name Region ID
1 Ludhiana 1
2 Amritsar 1
3 Bilaspur 2
4 Shimla 2
5 Hamirpur 2
11 Calicut 6
12 Cochin 6
13 Munnar 6
14 Patiala 1
31 Anantnag 13
32 Srinagar 13
33 Ahmedabad 3
34 Udhampur 13
44 Surat 3
55 Baroda 3
61 Kolkata 5
62 Darjeeling 5
63 Baranagar 5
71 Patna 10
72 Nalanda 10
73 Vaishali 10
81 Guwahati 11
82 Digboi 11
83 Sibsagar 11
111 Bangalore 7
112 Mysore 7
113 Coorg 7
121 Hyderabad 8
122 Vishakhapatnam 8
123 Vijaywada 8
131 Pune 4
132 Mumbai 4
133 Nashik 4
141 Jaisalmer 9
142 Jodhpur 9
143 Bikaner 9
Figure 2.3 | Entities Zone, Region, Area, and Item.

Salesman
Salesman ID Salesman Name Area Code
1 A. P. Singh 1
2 K. N. Kapoor 1
3 R. K. Chopra 2
4 P. G. Singh 2
5 S. N. Pathan 3
6 R. K. Khan 3
11 S. R. Trivedi 4
12 P. K. Jain 4
21 T. P. Khan 5
22 A. R. Khan 5
29 D. C. Khanna 31
30 P. T. Mehra 31
51 A. K. Garoo 34
52 D. N. Brave 34
61 T. N. Khan 32
62 A. P. Mishra 32
101 P. K. Damani 141
102 A. R. Agrawal 141
109 P. F. Karnik 131
110 A. M. Panzade 131
111 S. R. Sukhadiya 143
112 V. R. Jain 143
123 S. D. Sharma 142
124 K. K. Jain 142
145 S. E. Tendulkar 132
146 V. V. Manjrekar 132
147 P. N. Khedekar 132
165 A. R. Narayan 112
175 R. Benerjee 61
176 S. Tagore 61
178 L. M. Srinivasan 113
183 T. Ray 62
184 M. Ghosh 62
187 F. Srivastava 63
188 V. Jain 71
189 T. Chaterjee 71
190 S. B. Pillai 12
191 A. R. Nair 11
221 K. Yadav 81
222 G. F. Mishra 133
223 J. J. Raina 133
231 T. R. Naik 44
232 S. V. Joshi 44
261 A. F. Ghoshal 13
271 M. N. Shah 33
272 T. N. Sanghvi 33
273 A. A. Pathak 33
281 S. G. Gupta 55
282 K. D. Mistry 55
331 S. Chattopadhyay 82
81 D. Mathur 83
991 S. Mudaliar 111
Salesman No. Item No. Total_Qty_Sold
1 1 2
1 2 1
1 3 2
2 1 2
2 2 2
3 1 2
3 3 2
4 1 4
4 3 5
5 1 4
5 2 3
6 4 2
6 5 3
11 1 2
11 5 7
12 2 3
12 3 4
29 3 2
29 4 4
30 1 4
30 2 3
51 4 3
51 5 2
52 1 10
52 2 3
52 3 1
52 4 7
52 5 3
61 1 1
62 3 2
62 5 2
101 1 2
102 2 3
109 4 3
110 5 2
111 1 3
112 1 3
123 3 2
124 4 1
145 1 1
146 1 2
147 4 3
165 2 3
175 1 3
176 1 5
178 1 2
183 1 1
184 2 2
187 2 2
188 2 2
189 1 1
Figure 2.4 | Entities, Salesman, and Sales.

24 | Chapter 2
●
● The entities as shown in Tables 2.3 and 2.4 are related with the following relationships:
○
○ Each Zone contains many Regions (1 Zone–Many Regions)
○
○ Each Region contains many Areas (1 Region–Many Areas)
○
○ Each Area contains many Salesman (1 Area–Many Salesman)
○
○ Each Salesman sells many Items, and each Item is sold by many Salesman. (1 Salesman–
Many Items and Many Salesman–1 Item, i.e., many-to-many relationship between
Salesman and Item).
●
● Figure 2.5 shows the hierarchical model which represents the entities of Figures 2.3
and 2.4.
●
● Hierarchical data model can represent one-to-many relationships very effectively, but it
is not possible to represent many-to-many relationship because a child can have only one
parent in hierarchical model.
●
● To solve this problem, many-to-many relationship should be represented as two indepen-
dent trees. For example, to represent the relationship, ‘Each Salesman sells many Items
and each Item is sold by many Salesmen.’; the first tree will have Salesman as parent and
Item as child, and the second tree will have Item as parent and Salesman as Child. These
two different scenarios are shown in Figures 2.6(a) and 2.6(b).
●
● The hierarchical data model has the following advantages and disadvantages.
Advantages:
1. It is easy to understand.
2. The one-to-many relationship can be handled quite effectively.
Disadvantages:
1. It is not possible to insert a dependent record without inserting a parent record. For ex-
ample, as shown in Figure 2.6(b), it is not possible to insert the details of any item until
it is been sold by any Salesman. Similarly, as shown in Figure 2.6(a), it is not possible to
insert the details of any Salesman until he supplies any item.
Figure 2.5 | The hierarchical model.
1
2
Level 0 - Root Segment: ZONE
Level 1: Child
Segment: Region
Himachal Pradesh Jammu Kashmir
Ludhiana Amritsar Patiala Level 2: Child
Segment: Area
Level 3: Child
Segment: Salesman
Level 4: Child
Segment: Items Sold
A. P. Singh K. N. Kapoor R. K. Chopra P. G. Singh
Bulldozer Soil Stabilizer Stomper
Quantity
sold
North
1
1
1
1 2 2 1
2 3 4
2 14
3
Punjab
3 2

A. P. Singh
K. N. Kapoor
R. K. Chopra
P. G. Singh
S. N. Pathan
S. R. Trivedi
D. N. Brave
T. N. Khan
P. T. Mehra
S. E. Tendulkar
V. V. Manjrekar
P. K. Damani
S. R. Sukhadiya
V. R. Jain
G. F. Mishra
J. J. Raina
A. A. Pathak
T. N. Sanghvi
T. R. Naik
A. F. Ghoshal
R. Benerjee
S. Tagore
T. Ray
T. Chaterjee
K. Yadav
S. Chattopadhyay
1
2
2
2
4
4
2
10
1
4
1
2
2
3
3
1
2
1
1
2
3
2
3
5
1
1
3
4
Bulldozer
L. M. Srinivasan
A. P. Singh
K. N. Kapoor
R. K. Chopra
P. G. Singh
S. N. Pathan
D. N. Brave
A. P. Mishra
D. C. Khanna
S. D. Sharma
S. G. Gupta
A. R. Nair
S. B. Pillai
3
2
2
5
5
3
4
1
2
2
2
2
4
1
A. P. Singh
K. N. Kapoor
S. N. Pathan
S. R. Trivedi
D. N. Brave
P. T. Mehra
P. K. Jain
P. K. Jain
2
1
2
3
6
3
3
3
3
2
3
3
3
2
2
2
4
Soil Stabilizer Stomper
Excavator Dump Truck
A. P. Mishra
A. M. Panzade
S. Mudaliar
Quantity
A. R. Agrawal
M. N. Shah
S. V. Joshi
K. D. Mistry
A. R. Narayan
M. Ghosh
F. Srivastava
V. Jain
D. Mathur
R. K. Khan
A. K. Garoo
A. K. Garoo
D. N. Brave
D. C. Khanna
P. F. Karnik
P. N. Khedekar
K. K. Jain
4
2
3
7
4
1
3
3
R. K. Khan
S. R. Trivedi
D. N. Brave
4
3
7
2
3
2
2
1
(a)
Bulldozer
A. P. Singh
Soil Stabilizer
Stomper
1
2
1
2
Bulldozer
K. N. Kapoor
Soil Stabilizer
Stomper
2
2
2
5
Quantity
(b)
Figure 2.6 | (a) A tree representing item supplied by various salesman; (b) A tree representing
salesman supplies various items.

26 | Chapter 2
2. If we delete any root segment, then the dependent segments which falls under it, are also
deleted. For example, refer to Figure 2.6(a), if we delete root segment of the item Bulldozer,
then all the Salesmen, who have supplied Bulldozer, will also be deleted. As a result, the
Salesman who has sold only Bulldozer will be permanently deleted from the hierarchy
model. His record will be inserted again, only when he will supply some other item.
3. It is difficult to update any Child segment. As the number of segment increases, the tree
becomes extremely complex.At that time, it is very cumbersome to search for any segment
and update it, i.e., to search the last dependent segment of the last root segment of a tree,
one has to traverse all the dependent segments of all the root segments.
4. The hierarchical model can represent only the one-to-many (1: M) relationship. Here, the
many-to-many relationship causes redundant data.
2.3 | Network Data Model
●
● The Network data model represents data using link between records. The parent record
is called Owner Record, and the child record is called Member Record. If the Owner
and Member records are related with the many-to-many relationship, then they are con-
nected through connector record which is known as Set. The entities, given in Figures 2.4
and 2.5, are represented as a network model as shown in Figure 2.7.
●
● Figure 2.7 shows part of a network model, where:
○
○ Zone records are Owner records of Region records and Region records are Member
records.
○
○ Region records are Owner records of Area records, and Area records are Member re-
cords of Region.
○
○ Area records are Owner records of Salesman records, and Salesman records are
Member records of Area.
○
○ Salesman records are Owner records of Item records, and Item records are Member
records of Salesman which are connected through the ‘Set’ Sales. Sales record is a con-
nector record between Salesman and Item.
Bulldozer 200000 Soil Stabilizer Stomper 350000
North
1
Punjab HP J K
1
Ludhiana
1
2 3
Amritsar
2 Patiala
14
A. P. Singh
1 K. N. Kapoor
2 R. K. Chopra
3
1 1 2 1 2 1 1 3 2
1 2 3
P. G. Singh
4
300000
Figure 2.7 | The network model.

●
● The Owner record is linked with the first Member record, the first member record is
linked with the second Member record, and the second Member record is linked with the
third Member record, and so on up to the last Member record. The last Member record is
again linked with the Owner record. Management of the many-to-many relationship in a
network model is quite simple.
●
● Following are the advantages and disadvantages of a network model.
Advantages:
1. The many-to-many relationships can be represented more easily in a network data model
than that of a hierarchical data model.
2. The network data model supports Data Definition Language and Data Manipulation
Language.
3. To insert data of a new Item, say item no. 6, we would need to create a new Item record.
There will be no connector record for the new Item until it is sold by any Salesman. Item
no. ‘6’ will contain a single link from Item no. ‘6’ to Item no. ‘6’ itself, initially.
Disadvantages:
1. Searching is more complicated than hierarchical model in network model because of its
complex data structure.
2. The DML is also very complex as there are many constructs, such as records and links.
2.4 | Relational Data Model
The concept of relational model was given by E. F. Codd, in 1970, in his landmark paper on
relational data model. In the relational model, data are represented in a tabular form which is
called, relation (table), and they are associated with relationships. Therefore, the name of this
model is relational data model. Each entity is converted into relation and association is handled
through primary and foreign keys. The detailed explanation of relational model is given in
Chapter 3. Each entity occurrence is known as tuple (record) and characteristic of an entity
is called an attribute (column). It is very easy to represent many-to-many relationship using
relational data model. The relational model is widely used worldwide, nowadays, to store data.
Figures 2.8 and 2.9 show the relational model of data as shown in Figures 2.3 and 2.4. All the
relations are associated, with each other as listed here:
●
● Relation Zone is related with Region through ‘zone id’.
●
● Relation Region is related with Area through ‘region id’.
●
● Relation Area is related with Salesman through ‘area code’.
●
● Relation Salesman is related with Sales through ‘salesman id’.
●
● Relation Item is related with Sales through ‘item id’.
For relations:
●
● Zone—‘zone id’ is a primary key which is referred in Region relation.
●
● Region—‘region id’ is a primary key which is referred in Area relation, and ‘zone id’ is
referenced from Zone relation in Region relation.
●
● Area—‘area code’ is a primary key which is referred in Salesman relation and ‘region id’
is referenced from Region relation in Area relation.

28 | Chapter 2
●
● Salesman—‘salesman id’ is a primary key which is referred in Sales relation and ‘area
code’ is referenced from Area relation in Salesman relation.
●
● Sales—Combination of ‘salesman id’ and ‘item id’ is a primary key. ‘Salesman id’
is referenced from Salesman and ‘item id’ is referenced from Item relation in Sales
relation.
Region
Region ID Region Name Zone ID
1 Punjab 1
2 Himachal Pradesh 1
3 Gujarat 4
4 Maharashtra 4
5 West Bengal 2
6 Kerala 3
7 Karnataka 3
8 Andhra Pradesh 3
9 Rajasthan 4
10 Bihar 2
11 Assam 2
13 Jammu and Kashmir 1
Zone
Zone ID Zone Name
1 North
2 East
3 South
4 West
Item
Item No. Item Desc. Price (in `)
1 Bulldozer 200000
2 Soil Stabilizer 300000
3 Scraper 350000
4 Excavator 200000
5 Dump Truck 150000
Area
Area Code Area Name Region ID
1 Ludhiana 1
2 Amritsar 1
3 Bilaspur 2
4 Shimla 2
5 Hamirpur 2
11 Calicut 6
12 Cochin 6
13 Munnar 6
14 Patiala 1
31 Anantnag 13
32 Srinagar 13
33 Ahmedabad 3
34 Udhampur 13
44 Surat 3
55 Baroda 3
61 Kolkata 5
62 Darjiling 5
63 Baranagar 5
71 Patna 10
72 Nalanda 10
73 Vaishali 10
81 Guwahati 11
82 Digboi 11
83 Sibsagar 11
111 Bangalore 7
112 Mysore 7
113 Coorg 7
121 Hyderabad 8
122 Vishakhapatnam 8
123 Vijaywada 8
131 Pune 4
132 Mumbai 4
133 Nashik 4
141 Jaisalmer 9
142 Jodhpur 9
143 Bikaner 9
Figure 2.8 | Relations Zone, Region, Area and Item.

Sales
Salesman ID Item ID Total_qty_Sold
1 1 2
1 2 1
1 3 2
2 1 2
2 2 2
3 1 2
3 3 2
4 1 4
4 3 5
5 1 4
5 2 3
6 4 2
6 5 3
11 1 2
11 5 7
12 2 3
12 3 4
29 3 2
29 4 4
30 1 4
30 2 3
51 4 3
51 5 2
52 1 10
52 2 3
52 3 1
52 4 7
52 5 3
61 1 1
62 3 2
62 5 2
101 1 2
102 2 3
109 4 3
110 5 2
111 1 3
112 1 3
123 3 2
124 4 1
145 1 1
146 1 2
147 4 3
165 2 3
175 1 3
176 1 5
178 1 2
183 1 1
184 2 2
187 2 2
188 2 2
189 1 1
Salesman
Salesman ID Salesman Name Area Code
1 A. P. Singh 1
2 K. N. Kapoor 1
3 R. K. Chopra 2
4 P. G. Singh 2
5 S. N. Pathan 3
6 R. K. Khan 3
11 S. R. Trivedi 4
12 P. K. Jain 4
21 T. P. Khan 5
22 A. R. Khan 5
29 D. C. Khanna 31
30 P. T. Mehra 31
51 A. K. Garoo 34
52 D. N. Brave 34
61 T. N. Khan 32
62 A. P. Mishra 32
101 P. K. Damani 141
102 A. R. Agrawal 141
109 P. F. Karnik 131
110 A. M. Panzade 131
111 S. R. Sukhadiya 143
112 V. R. Jain 143
123 S. D. Sharma 142
124 K. K. Jain 142
145 S. E. Tendulkar 132
146 V. V. Manjrekar 132
147 P. N. Khedekar 132
165 A. R. Narayan 112
175 R. Benerjee 61
176 S. Tagore 61
178 L. M Srinivasan 113
183 T. Ray 62
184 M. Ghosh 62
187 F. Srivastava 63
188 V. Jain 71
189 T. Chaterjee 71
190 S. B. Pillai 12
191 A. R. Nair 11
221 K. Yadav 81
222 G. F. Mishra 133
223 J. J. Raina 133
231 T. R. Naik 44
232 S. V. Joshi 44
261 A. F. Ghoshal 13
271 M. N. Shah 33
272 T. N. Sanghvi 33
273 A. A. Pathak 33
281 S. G. Gupta 55
282 K. D. Mistry 55
331 S. Chattopadhyay 82
81 D. Mathur 83
991 S. Mudaliar 111
Figure 2.9 | Relations salesman and sales.

Exploring the Variety of Random
Documents with Different Content

He paused for effect.
“If she’ll let you,” put in Catherine, from no apparent motive.
He appeared ruffled.
“Oh, of course,” he said, “if she’ll let me. Of course. How could I
otherwise? ... Look at that elephant: those boys have given him a
bath bun.”
He seemed to think he had been sufficiently confidential.
“It’s nice to feel you’ve got a bit of capital behind you,” he said
smugly, and Catherine replied: “Yes, very nice.”
Then he developed a spurious boisterousness.
After tea they walked round all the open-air portions of the
establishment. One of the elephants picked up coins off the ground
and put them in his keeper’s pocket. Mr. Hobbs threw down a penny.
“Clever animal,” he remarked, after the trick had been
successfully performed, “but I expect the man keeps the money.”
“I daresay he does,” said Catherine.
Outside the monkey enclosure he said: “I suppose we were all
like this at one time.... Swinging from trees by our tails. That’s what
Darwin said, didn’t he?”
Afterwards, in Regent’s Park, he became himself again. At
Portland Road Underground Station he bought an evening paper
and consulted its inside page minutely.
“My shares,” he announced, sotto voce, as they sat together in
the train, “are now worth six hundred and sixty pounds. Another rise,
you see.... Nothing like money for making money, is there?”
“No,” she replied distantly....
When Catherine got back to Cubitt Lane, Amelia said:
“Well—had a good time?”
There was something so spiteful in Amelia’s tone that Catherine
felt compelled to say: “Oh yes, rather! Had a lovely time! And Mr.

Hobbs was awf’ly nice!”
§ 7
She was in a groove now. The rebuilding of her soul no longer
troubled her. She was content to be as she was. Her egoism, her
insane self-conceit fell from the lofty plane which had been their sole
excuse, and worked in narrower and more selfish channels. In Cubitt
Lane she was considered proud and “stuck-up.” She did not
associate with the “young fellers up the road,” nor did she frequent
the saloon-bar of the King’s Head. In all things she was quiet, aloof
and unimpeachably respectable. She was always dressed neatly
and well, and she did not possess any dress which, by its showiness
and general lack of utility, bore the label “Sundays only.” Now that
she was in a district where fine talk was unusual, she began to be
vain of her language and accent. To Amelia she was always scornful
and consciously aloof: even to Mr. Hobbs she was not loth to betray
an attitude of innate superiority. And Mr. Hobbs did not mind it. The
more arrogant her mien, the more scornful her tone, the more he
singled her out for his preferences and favours.
The Duke Street Methodist Chapel, despite its frowsy
surroundings, had always been famous as the last refuge of
unimpeachable respectability. Its external architecture was as the
respectability of its patrons, severe and uncompromising. And the
Reverend Samuel Swallow, excellent man though he was, did not
fulfil the ideal of a spiritual guide. His sermons were upright, and as
often happens, stiff-necked as well. There was too much noise and
bombast about him. Too much chumminess in his dealings with the
Almighty. Catherine went to one Sunday evening’s service, and
those were her mental criticisms. She sat in one of the front pews,
and exhibited her superiority by dropping a sixpence gently on to a
pile of coppers when the plate came round. The building had
recently been re-decorated, and stank abominably of paint. In the
choir, where years ago her mother had stood and yelled, a new
galaxy of beauty sang down menacingly over the shoulders of the
Rev. Samuel Swallow.... And before the sermon the latter

announced: “Whan of our brethren has presented us with a
timepiece, which, as you may perhaps have noticed, is now fixed
immediately beneath the rails of the gallery.” (General craning of
necks and shuffling of collars to look at it.) ... “I trust—indeed, I am
sure—that none of you will show your impatience towards the
conclusion of my sermon by looking round too frequently at this
recent addition to the amenities of our church....” A soft rustling titter,
instinct with unimpeachable respectability....
Catherine decided that she could not join a “place” like that. She
had decided to join a “place” of some sort, because joining a “place”
was an indispensable item of respectability. But she wanted her
respectability to be superior to other people’s respectability, superior
to Amelia’s, superior to Mrs. Lazenby’s, superior to the Rev. Samuel
Swallow’s. Her conceit now wanted to make her more respectable
than any other person she knew.
She asked Mr. Hobbs if he belonged to a church.
He replied: “I am afraid, my time and avocations do not permit me
to attend regularly at any place of worship.... But I often go to the
City Temple.... I consider religion an excellent thing....”
She determined to be more respectable than Mr. Hobbs.
“Of course,” she said freezingly, “I am Church of England....”
§ 8
The Bockley Parish Church was large, ancient and possessed an
expensive clientele. Into this clientele Catherine entered. Her
entrance was not at first noticed. She rented a seat, carried her
hymn and prayer-books piously to and from the service, and
purchased a second-hand hassock at a valuation off the previous
occupant. The Rev. Archibald Pettigrew shook hands with her
occasionally, and raised his hat if he passed her in the street. At a
church concert she volunteered as accompanist for some songs, but
her professional efficiency did not attract attention.

One of the curates, fresh from Cambridge, saw her and took
notice. He was very youthful and very enthusiastic; secretly ritualist,
he dabbled in music, and indulged in unseemly bickerings with the
organist and choirmaster. He wanted the choir to sing like the choir
at King’s College, Cambridge. He would have liked to deliver a Latin
grace at the annual boys’ outing to Hainault Forest. In most of these
things the Rev. Archibald Pettigrew exerted a restraining influence
upon him. But in Catherine the young enthusiast thought he saw a
kindred spirit. This young woman, so quiet, so demure, so earnest
and pious in her religious observances, was she not destined to be
his helper and confidante?
He lent her tracts and showed her some candlesticks he had
purchased in Paternoster Row. And frequently he came to Cubitt
Lane and produced an overwhelming impression on Mrs. Lazenby
by giving her a visiting card inscribed with:
The Rev. Elkin Broodbank, St. Luke’s Vicarage, Bockley.
And Catherine was unspeakably charmed and flattered by his
attentions. But she was not impressed by his personality. He had
none....

CHAPTER XXIII
ONCE AGAIN
§ 1
ON the Monday morning exactly a week before the August Bank
Holiday, Catherine unpacked the morning’s music with a quiet
satisfaction that knew no bounds. She was by this time a changed
woman. No longer impetuous and hasty, no longer fiery and
passionate, no longer a creature of mood and fancy: she was quiet,
restrained, dignified almost to the point of arrogance, immensely
reliable, and becoming a little shrewd. She had earned the reputation
of being an expert saleswoman. There was scarcely a piece of
music, or a song, or an orchestral setting which she did not know of:
she was a mine of recondite information about violin obligatos and
harp accompaniments and so forth. Even Mr. Hobbs, who had
hitherto passed as a paragon, acknowledged in her a superior. His
mind was merely a memorized and remarkably accurate music
catalogue: hers was full of scraps of another world, scraps that
raised her above her fellows. Never, even in her greatest days, had
her superiority seemed so incontestable as now. Never had she
been so quietly proud, so serenely confident that the deference
accorded her was no more than her due.
As she untied the string round a bulky parcel of new ballad songs
she reflected upon her own unconquerable supremacy. Over in the
gramophone department was Amelia, sorting a new consignment of
records. Amelia looked as usual, sullen and morose. And it gave
Catherine a curious satisfaction to see Amelia looking sullen and
morose. Partly, no doubt, because it threw into vivid relief her own
superb serenity. But there was another reason. Amelia’s moroseness
had a good deal to do with Catherine’s relations with Mr. Hobbs.

There had been a time when Mr. Hobbs had seemed to be showing
Amelia a significant quantity of his attention. Not so now. To
Catherine he gave all the attention he had previously bestowed upon
Amelia, coupled with a deference which he had never offered to
Amelia at all. Amelia felt herself deposed from a somewhat
promising position. But it was not Catherine’s fault.... Catherine
never encouraged Mr. Hobbs. She gave him piquant rebuffs and
subtle discouragements, and frequent reminders that she was
superior to him. She was always distant and unresponsive, and
sometimes a little contemptuous. But the more did he return to the
assault. Her superb aloofness enchanted him. Her pride, her royal
way of taking homage as no more than her due, her splendid self-
aplomb convinced him that this was the woman to be Mrs. Hobbs....
So Catherine did not encourage him. It would have been rather silly
to do so. And as she saw Amelia looking so sullen and morose, she
thought: “Foolish creature! Fancy her thinking that I’m cutting her
out! Why, who could help preferring me to her? And I have never
encouraged him, I’m quite sure of that ... I’m not a bit to blame....”
On the desk beside her was a single sheet of writing-paper
inscribed with the handwriting of Mr. Hobbs. It was his day for visiting
publishers, and it was evident to Catherine that he must have gone
considerably out of his way to come to the shop and leave this note
for her. And to induce Mr. Hobbs to go out of his way was to create a
revolution in his entire scheme of existence. Well did Catherine know
this, and as she read she smiled triumphantly.
dear miss weston,
Don’t forget to repeat the order if those songs from Breitkopf and
Härtel don’t arrive. I shall be back about three this afternoon.
Yrs. sincerely,
j. a. hobbs.
and—
P.S.—Are you free next Saturday afternoon? If so, we could go to
Box Hill and Reigate.
Catherine, therefore, smiled triumphantly.

There was absolutely no need whatever for him to remind her to
repeat the order. That was part of the ordinary routine of her
business. He knew she would do that: his reminder had been merely
an excuse for something upon which to hang a P.S. Silly man!—Did
he imagine such a transparent subterfuge could deceive her?
She did not particularly like him. He was not more to her than any
other man. But she liked him to like her. She liked the sensation of
entering the settled calm and ordered routine of his existence and
exploding there like a stick of dynamite. He had faults. He was too
careful with his money, too prone to give money a higher place than
it deserved. And his mind, when he strove to divert it into
philosophical channels, was woefully sterile. But he so obviously
reverenced her. With a quiet dignity he demanded to be treated as
an inferior. There was no resisting such an appeal. Whether she
liked him or not she could not help liking the immense compliment he
paid her by his whole attitude.... It was not that he had not a high
opinion of himself. He had, and that enhanced the significance of the
fact that his opinion of her was higher still....
Next Saturday afternoon? ... Yes, no doubt she would be free
next Saturday afternoon....
§ 2
As the morning progressed she transacted her business steadily
and methodically. About three in the afternoon Mr. Hobbs returned.
She was careful to show no eagerness to see him, careful that she
should not betray by her countenance or manner her reply to his
invitation. He, on his part, was quite ready to fall in with her pretence.
He attended to various matters in the gramophone department and
left her very much to herself. When he spoke to her it was strictly on
business, and with a frigid professional politeness.
At a few minutes past four he called her to the telephone. A
gentleman wanted a piece of music, and he did not know what
exactly it was or where it could be obtained. Perhaps Miss Weston
would oblige....

Catherine went to the instrument.
It tickled her vanity to be appealed to as a last resource. She
tossed her head a little proudly as she put her ear to the receiver.
A strange thing happened....
Someone was speaking down the instrument, and at the sound of
his voice Catherine flushed a deep red. A wave of recognition and
recollection and remembrance swept over and engulfed her. She did
not hear what he said.
“Again, please,” she muttered huskily, in a tone not in the least
like her usual, “I didn’t quite catch....”
The voice boomed in rather irritated repetition,
“Bach double-piano concerto,” it said, “in C minor.... Bach ... for
two pianos ... do you understand?”
She tried to grasp it while her mind was busied with a million
other things.
“It goes like this ...” the voice went on, and commenced a weird
nasal rumble like a tube-train emerging from a tunnel.... “Da-da-da-
da-da-daddaddadd-addadd-addah.”
She smiled! Once again fate had flung to her a moment of
triumph. Long ago, when the man at the other end of the telephone
had been her friend, she had learnt specially for him a work of Bach
which was little known and not likely to be much cared about. Her gift
had never been offered.... And now, after all this interval, he was
enquiring about the very piece she had learned for him!
She put the telephone apparatus on the top of the piano on which
she tried things over. Then sitting down she played over the first few
bars of the concerto.... Keeping the receiver to her ear she heard:
“That’s it!—That’s the one!—Do you know it?—Curious—well,
well, get it for me, will you.... Good!—I’ve tried all over town for it....”
“What address?” she enquired mechanically.

The voice replied: “Professor Verreker ... Seahill ... Barhanger,
Essex.”
As she walked back to the counter Mr. Hobbs said: “Did you
know what the gentleman wanted?”
“Yes,” she replied fiercely, triumphantly, contemptuously. He
stared at her. He did not know that a change had passed swiftly over
her. He did not know that the sound of a man’s voice spoken over
fifty miles had swept her out of the calm seas into the wind and rain
and storm. He did not know that once again she was in deep and
troubled waters, fighting for life and a sure footing. He thought his
invitation had offended her. He made haste to apologize.
“I hope,” he began, “you didn’t mind me asking you to Box——”
“I’m afraid,” she replied impatiently, “I can’t come ... I’ve ... I’ve
another engagement....”
And he went away into the gramophone department....
§ 3
The knowledge that Verreker was in England, within
approachable distance of her, gave her a strange, complicated
mixture of pleasure and annoyance. Deep down in her heart she
knew that to see him again would be as a breath of life after ages of
dim existence. Yet she was annoyed, because she had grown to be
satisfied with the dull, drab routine of her days: she had built up a
new, and on the whole satisfactory scheme of existence on the
supposition that she should never see him again. She did not want to
see him again. She did not want to have anything to do with him.
And yet she knew that some day either circumstances or her own
initiative would bring her face to face with him once more.... She
knew that his place in her life had not achieved finality, that there
was more to say and to hear, and great decisions to be made.
Secretly she knew that some day, when the impulse seized her,
she would go to visit him at Barhanger. But with amazing credulity
she told herself: Of course I shall never go to see him. If he cares to

ask me I will come. But he must take the initiative, not I.... But she
began to picture their meeting. She began to conjure up images of
Seahill and the Essex countryside and he and she walking and
talking amidst a background of her own imagining. Just as in the old
days she had invented an “ideal” conversation to be pursued at any
surprise meeting with her father, so now she concocted a special
dialogue between herself and Verreker, which, if he should only play
the part allotted to him, would reveal her in an attractive and
mysterious light. Of course he would not do so: of that she was quite
certain, yet the manufacture of ideal rôles for him and herself gave
her a good deal of restricted pleasure. She must at this time have
decided definitely to go and see him, otherwise there could have
been no inducement for her to dream dreams. But she still told
herself that she would not see him till he had seen her.... One
evening she visited the reference department of the Bockley
Carnegie library and consulted a map of Essex. Barhanger was
almost on the sea-coast; five miles from the nearest railway station,
overlooking one of the great tidal estuaries of the Essex rivers. And
Barhanger Creek reached right up to the village of Barhanger.... She
had not thought it was so near the sea. She had pictured an inland
village with a village green and thatched cottages and perhaps a
single-line railway station. Now she had to dream her dreams over
again in a different setting, and into this new setting came the creek
and the broad estuary and the shining sea, all magnificently
idealized, all transfigured by the presence of herself and Verreker....
It was curious how the thought of him awoke in her old dreams
and aspirations. She began once more to revile her own soul for its
selfishness and avarice: she began to wish for her old pianoforte
prowess and such education as she had once managed to cram into
that head of hers. Yet against her will was all this change and flurry:
she was always protesting, I am better as I am. I want to be quiet
and respectable. I don’t want to see him or to know him, because he
has unlimited power to make me unhappy....
Her superb serenity left her. She became once more a foolish,
unreliable creature of fierce trivialities. She no longer took any
interest in the affairs of Amelia and her mother and Mr. Hobbs. She

began to think rather acutely of Helen, though. How would Helen
come into the matter? Would Helen be jealous of her interference?
... And did he love Helen? Or was it only a marriage of convenience?
All those things she would never find out unless she visited him.
Though, of course, she would not visit him without an invitation. That
was quite decided.
On the Saturday morning before the August Bank Holiday Mr.
Hobbs left a note for her on her desk. She slipped it in her hand-bag
without opening it.... She was concerned with other things. And when
she got home on Saturday afternoon she discovered on her table a
card left by the Rev. Elkin Broodbank, of St. Luke’s Vicarage,
Bockley. This also she dropped unceremoniously into her hand-
bag.... She was concerned with other things.... She next took up an
A.B.C. railway guide, and searched it carefully for some minutes.
Then she shut it with a bang and went to her bedroom to decorate
herself. She was not so charming as she once had been, and so the
process of decoration became a longer one. Her hair—the thing of
her she most prized—had begun to be dull and lack-lustre: the eyes,
too, had lost vivacity. She was no longer a young woman.... Oh, the
horror of growing old, when youth has taken charm away! ... But she
was concerned with other things. She scribbled a note to Mrs.
Lazenby and left it on the kitchen table. Then she walked discreetly
down the steps into Cubitt Lane, and by way of Makepeace Common
to Bockley Station....

CHAPTER XXIV
THE LAST PHASE
§ 1
ON the Colchester and Ipswich train it was still possible for her to
think. I am not necessarily going to Barhanger. I have a ticket to
Holleshont, and there are many places one can get to from
Holleshont besides Barhanger. Besides, even if I do get to
Barhanger, Barhanger is no doubt an ideal place in which to spend a
Bank Holiday week-end. There is no earthly reason why I shouldn’t
go to Barhanger. It is close to the sea, and I need a holiday....
And secretly she rejoiced at the ecstasy of the thought: I am
going to see him. Whatever he says or does, whatever the issue
may be, whatever I suffer then or afterwards, I shall see him.... As
the train rolled over the drab eastern suburbs she revelled in the
sensation that every throb and pulsation of the wheels narrowed the
distance between herself and him.... And withal came another part of
her answering her coldly, reprovingly: You are silly to go on this fool’s
errand. You are losing the satisfaction and contentment it took you
so long to acquire. Where now is your ambition to lead a quiet,
sedate and respectable life, without the storm and stress of
emotional escapades? Where now in your mind’s perspective are
Mr. Hobbs and the Rev. Elkin Broodbank? Oh, you fool! you will
suffer, and it will be your own fault. You will have the old slow fight
over again, you will have to build up your contentment right from the
bottom.... Oh, you fool! ... And still her heart answered: I don’t care. I
am going to see him.... I am going to see him....
Between Romford and Chelmsford she remembered the
unopened letter that she had in her hand-bag from Mr. Hobbs. She

tore it open and read it. It was a strange mixture of hopeless
adoration and ruffled dignity.
my dear miss weston,
I am very sorry indeed if my invitation for Saturday offended you.
I am glad to think your reason for declining it is that you had another
engagement to fulfil. In the circumstances, is it too impertinent of me
if I invite you to spend the Bank Holiday on the Surrey Hills? I know
the district pretty well, and am sure you will enjoy the fine scenery as
well as the invigorating air. There is a motor omnibus service as far
as Reigate, and we could get from there to a number of interesting
spots. Hoping you will be able to come with me.
Believe me,
Yours sincerely,
j. a. hobbs.
She smiled wanly upon the drearily angular handwriting. In
rummaging in her hand-bag she had come across the Rev. Elkin
Broodbank’s visiting card, left by him that morning, and she caught
sight of some writing on the back which she had previously
overlooked. “I find you not in,” the Rev. Elkin had written, in his
finicky handwriting and pseudo-Carlylean prose style, “so I leave
this. Will you have tea with me on Sunday? I have old MSS. church
rubric to show you: also good booklet on Oxford movement.—Yrs.,
E. B.”
Also upon this she smiled wanly....
Chelmsford....
Oh, what have I done with my life? she cried to herself in a
moment of sudden horror. What have I to show for all these years of
toil and stress? Is there anything of all that I have ever had which
has lasted? I am twenty-four years old, and my youth is over. I have
had dreams, I have had ambitions, I have had golden opportunities
and been near success. But what have I to show? Have I any hold
on life which death would not loose? Am I deep set in the heart of
any friend, man or woman, in the world? Whatever happens to me,

does it matter to anyone save myself? No, no, and therefore I am
going to Barhanger. I would go to Barhanger if it cost me pain for the
rest of my life....
At the junction station midway between Chelmsford and
Colchester she got out. On the opposite platform the train for
Holleshont was waiting. Small and feeble it looked beside the great
express, but there was an air of sturdy independence about it, and
especially about its single track curving away over the hills into the
dim distance. Catherine breathed the country air with avidity: she
entered a compartment and leaned out of the window as the express
rolled slowly out of the other platform. As it vanished into the north-
east the station became full of broken silences and staccato sounds.
Glorious! she murmured, as the sun warmed her cheeks and the
wind wafted to her the scent of pansies growing on the embankment
near by. And then suddenly, as if it had a fit of divine inspiration, the
train moved off....
Over the dim hills, stopping at tiny halts, with waiting-rooms and
booking halls fashioned out of wheelless railway carriages, up steep
slopes where the grass grew long between the rails, curving into
occasional loops, and pausing sometimes like a hard-worked animal
taking breath. And then, from the top of a hill, the miles drooped
gently into the bosom of the estuary: the tide was out and the mud
shone golden in the sun. Yachts were lying stranded off the fair-way,
and threading the broad belt of mud the river ran like a curve of
molten gold. There were clusters of houses here and there on either
bank, and a church with a candle-snuffer tower, and stretches of
brown shingle.... And the train went gathering speed as it broke over
the summit....
At Holleshont the estuary was no longer in view, but the sea-
smell was fresh in the air. “Barhanger?” she said to a man with a
pony and trap who was waiting outside the station. He nodded, and
helped her to a seat beside him. He was buxom and red-faced and
jolly. If he had been younger, it would have been rather romantic to
go driving with him thus along the lonely country lanes. But he was
taciturn, and stopped once to pluck from the side of the hedge a long
grass to suck. At times he broke into humming, but it was a tune

Catherine did not recognize. After half an hour’s riding they came
upon a dishevelled country lane, which on turning a corner became
immediately the main street of a village. They passed a church and a
public-house, a post-office, a pump, and then another public-house.
At this last the driver pulled his horse to a standstill and indicated to
Catherine that she should descend. “Barhanger,” he muttered
explanatorily. Seeing her uncertainty, he questioned her. “Lookin’
f’ranywhere partic’ler, miss?”
She replied with a momentary impulse: “Seahill.”
He pointed in a southerly direction.
And now she was walking straight to “Seahill.” ...
The road narrowed into an ill-defined pathway and climbed
abruptly on to the top of the sea-wall. A long arm of the great shining
estuary lay stretched at her feet, and dotted about it were scores of
mud-banks overgrown with reeds and sea-lavender. The grasses
rose high as her knees, and she pushed through them and against
the wind till her cheeks were flushed with exertion. At the mouth of
the creek the estuary rolled infinitely in either direction, and miles
and miles of brown-black mud were hissing in the sunlight.
“Glorious!” she cried, and flung back her head proudly to meet the
wind that swept the corner of the creek. She turned to the right and
walked on swiftly. Behind her, looking quite near, but really a good
distance away, the village of Barhanger slept drowsily in the
afternoon heat: ahead the sea-wall swelled and rolled into great
meaningless curves. Not a human being besides herself occupied
the landscape. The mud hissed and cracked, and the grasshoppers
chattered and the wind shook the long grasses into waving tumult.
And over on the mudbanks the sea-gulls gathered and rose and
called shrilly, and swooped down again to rest....
At one point the land rose slightly inland from the sea-wall, and
perched on the crest of the low hill there stood an old-fashioned red-
bricked house with a litter of sheds and stabling around it. Something
told her that this was “Seahill.” A pathway wound upwards through
the long meadow-grass: the pale green streak over the darker green
told her that this was a method of approach used sometimes, but not

frequently. And there were ditches to cross—ditches banked with
mud, which at high tide must have been brimming with salt water....
§ 2
She found her way into a sort of courtyard formed by the back of
the house and surrounding outbuildings. And there, throwing food to
some chickens, was Helen!
“Cathie!” Helen’s voice was full of glad welcome. Helen had
grown a fine woman, somewhat stout perhaps, but upright and fine-
looking. She kissed Catherine affectionately, and in her quiet way
made a great fuss over her.
“How did you know we were here?” she asked, as she led
Catherine into the house by way of the kitchen.
“Quite by chance,” replied Catherine. “I just happened to hear
somebody mention it—somebody in the musical line.”
“Ah—my husband knows so many people, doesn’t he? And how
about your arm? Of course we heard all about that, you know——”
“Oh, that’s getting better again slowly. When did you come back
from America?”
“America?” Helen’s face showed a blank. “We never went to
America. Who told you that?”
Catherine flushed a little. “I don’t remember,” she replied
nonchalantly. “It must have been a wrong idea I picked up from
somebody.”
They chatted on for some time and then Helen said:
“Well, perhaps you would like to go and see my husband. He’s in
his study—straight up the steps and second on the left. He’ll be
working, but he’ll be glad to see you, I daresay. He used to be very
interested in you, didn’t he?”
“I’ll go up and see him,” replied Catherine quietly.

She ascended the steps and found her way to the door of his
study. With some trepidation she knocked....
§ 3
It was a large room facing the west. The sun shone drowsily on a
table littered with papers and opened books. There was the piano
which she had so often played in the music-room at “Claremont.”
There were the same bookcases, with glass doors swung open, and
the aperture between the tops of the books and the shelf above filled
with letters and papers. That had always been one of his untidy
habits. And scattered over all the available wallspace were
disconnected fragments of shelving, sagging in the middle if the
span were wide, and piled high with longitudinal and horizontal
groups of books. The old brown leather armchairs and the club-
fender occupied positions in front of the fireplace. The carpet was
thick, and littered here and there with the grey smudge of tobacco-
ash and scraps of torn paper that had escaped the meshes of the
basket. The scene was curiously similar to that on which she had
first seen him at “Claremont.” He was sitting in one of his armchairs
with an adjustable reading bracket in front of him. She could see
nothing of him, but a coil of rising smoke that straggled upwards from
the back of the chair told her that he existed. She had knocked on
the door before entering, and his voice had drawled its usual “Come
in.” He had heard the door open and close again, but he did not look
round. She knew this habit of his. Doubtless he would wait to finish
the sentence or maybe the paragraph he was reading. She came
across the intervening space and entered the limits within which his
eye could not avoid seeing her. The sun caught her hair and flung it
into radiance; she was glad of this, for it made her seem youthful
again.
She saw him for a fraction of a second before he caught sight of
her. And a strange feeling of doubt, of perplexity—might it be even of
disappointment?—touched upon her. He was the same, quite the
same. And yet—there was a sense in which he was not as she
expected. But she had not expected him to be very much changed. It

was only a passing phase that swept across her—hardly to be
understood, much less explained. But she felt it, and it surprised her.
When he saw her he opened his eyes very wide and stared.
Then he pushed back the book-rest and rose from his chair. All the
time she was watching him narrowly. There was a queer phase
during which neither of them moved or attempted to move. And then,
the tension becoming too great to be borne, she gave her head a
little toss and said: “Well?”
She had an absurd feeling of curiosity about his first words to her.
In her ideal dialogue with him he struck an attitude of surprise and
bewilderment and ejaculated, after the manner of the hero in a
melodrama: “What?—You!—You! Is it really you?”
Of course he did nothing like that. She might have expected her
fancied conversation to go all wrong from the start. He slowly and
cautiously held out his right hand, and smiled a careful, quizzical
smile.
And his first words were: “How are you?”
“Very well,” she replied mechanically.
There was a pause, after which he said: “Won’t you sit down?”
“Thank you,” she replied, and occupied the other armchair. He
still remained standing and smoking.
“I suppose,” he said reflectively, “you got the address from the
Directory?”
“No,” she replied nonchalantly, “it was quite by accident. I am one
of the assistants in the music department of Ryder and Sons, and
you yourself gave me your address over the telephone last Monday.”
“What a startling coincidence!” he muttered, as if by way of
comment to himself.
Pause....
“So,” he went on meditatively, “you were the young lady who
knew the Bach double-piano concerto from memory! Curious! ... I
thought it was remarkable, and the next time I was in town I intended

coming up to Ryder’s to see who you were.... Perhaps it is well I
didn’t.... We might have startled each other.”
“We might,” she said quietly.
Long pause....
“I don’t remember your ever playing the concerto when I knew
you,” he resumed, still in the rôle of a somewhat curious spectator. “I
never taught it you, did I?”
“No,” she answered. “I learnt it myself.” And there was just a
momentary gleam of fire within at that remark. As much as to say:
“Don’t think I am not capable of doing some things myself.”
“Do you know all of it?” he asked.
“I did—but I don’t know if I remember it all now.” He tapped his
pipe on the mantelpiece.
“I wish you’d play it for me,” he said, slowly and still meditatively,
“I should like very much to hear it ... and besides ... it would ... give
me time to think....”
“To think what?” she put in sharply.
He sat down, filled his pipe afresh and lit it, saying as he did so:
“Well—to think—one of the things, at any rate—why you have
come.”
There was something in the tone of that last remark of his which
stung her to the retort:
“So you think it is possible for me to go to the piano and play a
Bach concerto while you sit coolly down to wonder why I have
come?”
“Well,” he said, suddenly and with emphasis, “why have you
come?”
“You said if I was ever over in the States I was to come and see
you. I naturally expected that the invitation would extend to when you
returned to England.”

“Did it not occur to you,” he remarked slowly, “that when I
returned from the States I should have sent you my address if I had
desired to see you?”
“Of course,” she interposed neatly, “as it happens, I know that
you never went to America at all.”
He did not seem greatly ruffled by this.
“Then,” he continued, “you know that I told you a lie. And you
may have the satisfaction—if it is a satisfaction—of knowing also that
you are the only person in the whole world who has ever made me
do that. That honour,” he added bitterly, “you share with no one: it is
yours entirely.”
She felt: Now we are getting to it.
“I don’t know why it should have been so necessary for you to tell
me a lie,” she said.
“The fact is,” he announced brutally, “I wanted to get rid of you,
and that seemed the only way.”
She winced a little at his words, but interposed sharply:
“Why did you want to get rid of me?”
He grunted something incoherent, and began to walk towards the
door.
“Look here,” he said, “we’ll go for a walk. I’m not going to have
you quarrelling in here.”
“But surely we aren’t going to quarrel?”
“On the contrary, we are going to quarrel. We’re going to quarrel
most damnably.... Come on!”
He led her back down the steps into the kitchen. Helen was there
preparing a meal. As he passed he addressed her.
“Miss Weston and I are going out for a stroll along the sea-wall,
Helen.... We shan’t be long. Miss Weston has to get back to town to-
night, so she hasn’t got much time to spare.”

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