Content

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DataBases
Content 15.1 Basic features Types of database
Data structures 15.2 Creating a database Screen
layout Entering data Editing data 15.3 Displaying
data Searching Queries Sorting records 15.4
Create and print reports Creating a
report Printing a report
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• Outcomes
• By studying this chapter you should be able to
• create a database
• search and sort records in a database
• display data using a selective query
• design a variety of report formats to meet
  different needs.
• This chapter will help you to become a competent
  user of a database. It examines the basic
  features of databases and how to create a
  database. You will learn how to construct a
  query, how to create a report and how to modify a
  database

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• A database is an organised collection of data.
  People have used databases for many years, long
  before the advent of the computer. The telephone
  book is a database which is arranged
  alphabetically by family name. Another example is
  the traditional office filing cabinet.
• In recent years, computerised databases have been
  developed. There are three main reasons for this
• Computers are ideal tools for searching a large
  amount of data, quickly and accurately. A
  computerised database allows cross-referencing, a
  feature that is very complicated on paper
  databases.
• Computerised databases can be updated without
  having to type all the data. A huge amount of
  information can be stored on disks, revised and
  arranged as appropriate.
• A computerised database can divide the data into
  sections for particular applications.

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Databases are accessed by a database management
system (DBMS), a software package that builds,
maintains and provides access to a database (see
Figure 15.1). The DBMS allows you to choose which
data is required and how to display that
information in a meaningful way. Before the
advent of DBMS there was no alternative but to
create a database using high level languages like
COBOL, FORTRAN or C. Now, if a customised
database is not required, a database can be
created within a short amount of time using a
DBMS.
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Types of database A flat file database is the
simplest type of database. All its data is
contained in one file. Flat file databases are
used for simple structured tasks such as storing
personal names and address details. We examine
flat file databases in this book. Databases can
also be classified as a prepared database or an
empty database. A prepared database (closed
database) contains information about a specific
subject. Its data can be accessed and read, but
not changed. For example, a census on CD-ROM is a
prepared database. An empty database
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Data structures Data is the raw facts put into
the computer system, such as text and numbers.
This data is then processed by the computer. When
the data has been ordered and given some meaning,
it is called information. It is the result of
work on the computer and depends on the data
entered. Data is stored in data structures called
files, records, fields and characters. To
illustrate these data structures, consider the
telephone book as an example of a database (see
Figure 15.2). A file is a block of data. When you
have done some work on the computer it is stored
in a file. The L-Z telephone book would represent
a file. A file in a database is divided into a
set of related records
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A record is a collection of facts about one
specific entry in a database. Information about a
person in the telephone book is a record. A
record is divided into one or more related
fields. A field is a specific piece of data. The
family name, address and telephone number in the
telephone book are fields. A field is also known
as a data item or category and is made up of
characters. A character is the smallest unit of
data that people can handle and includes letters,
numerals and special symbols.
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1. Copy and complete the following
sentences. A is an organised collection of
data. A flat file database is the type of
database. A prepared database contains about a
specific subject. An empty database allows data
to be entered and (e) is the raw facts put into
the computer system, such as text and
numbers. A in a database is divided into a set of
related records. A is a collection of facts about
one specific entry in a database. A record is
divided into one or more related A is the
smallest unit of data that people can handle. 2.
Why have computerised databases developed in
recent years? 3. How do you access a database? 4.
What is the purpose of flat file databases? 5.
Explain the difference between a prepared
database and an empty database. 6. List the four
data structures used in databases.