1. Chapter 6 - DATABASE APPLICATIONS
AND IMPLICATIONS
2. 6.1 DATABASE BASICS
6.1.1 What Is Database?
A database can be thought of as a set of logically related
files organized to facilitate access by one or more
applications programs and to minimize data redundancy.
This concept does not imply that all data relating to a
company’s business should be contained on a single
database, but simply that all records in a database should
be related and that redundant data should be minimized.
Databases make it possible for people to store, organise,
retrieve, communicate, and manage information in ways
that wouldn’t be possible without computers.
3. Computerized databases offer several advantages over their
paper-and-pencil counterparts:
Databases make it easier to store large quantities of
information.
Databases make it easier to retrieve information quickly and
flexibly.
Databases make it easy to organize and reorganize information.
Databases make it easy to print and distribute information in a
variety of ways.
Database make it easier to incorporate changes easily and
quickly
Database provides data security from unauthorized use
4. 6.1.2 Database Anatomy
A database is composed of one or more files. A file is a
collection of related information; it keeps that
information together the way a drawer in a file cabinet
does. (The term file sometimes causes confusion because
of its multiple meanings. In this chapter, file refers
specifically to a data file created by a database program.)
A database file is a collection of records. A record is the
information relating to one person, product, or event.
Each discrete chunk of information in a record is called a
field.
The type of information a field can hold is determined by its
field type. For example, the author field in the library database
would be defined as a text field. The field specifying the number of
copies of a book would be defined as a numeric field. A date-of-
purchase field might be a date field.
5. 6.1.3 Database Operations
Browsing
The challenging part of using a database is retrieving
information in a timely and appropriate manner. One
way to find information is to browse through the
records of the database file just as you would if
they were paper forms in a notebook. Most
database programs include a variety of
commands and capabilities that make it easy to
get the information you need when you need it.
6. Database Queries
The alternative to browsing is to ask the database for
specific information. In database lingo, an
information request is called a query. A query may
be a simple search for a specific record or request
to select all of the records that match a set of
criteria. Once you’ve selected a group of records,
you can browse through it, produce a printout, or
do just about anything else you might do with the
complete file.
7. Sorting Data
Sometimes it’s necessary to rearrange records to make the
most efficient use of data. A sort command allows you
to arrange records in alphabetic or numeric order
based on values in one or more fields.
Printing Reports, Labels, and Form Letters
In addition to displaying information on the screen,
database programs can produce a variety of printouts. The
most common type of database printout is a report—an
ordered list of selected records and fields in an easy-
to-read form.
8. Database programs can also be used to produce mailing
labels and customized form letters. Most database
programs don’t actually print letters; they simply export or
transmit the necessary records and fields to word
processors with mail merge capabilities, which then
take on the task of printing the letters.
Complex Queries
Queries may be simple or complex, but either way they
must be precise and unambiguous. The exact method for
performing a query depends on the user interface of the
database software.
9. 6.1.4 Special-Purpose Database
Programs
Many specialised database programs are sold as directories,
geographic information systems, personal information managers
(PIMs), or electronic organisers, automating some or all of these
functions:
address / phone book
appointment calendar
to-do list
street atlas
miscellaneous notes
The user interface of personal information management software is
especially important because of the constant interaction between the
user a In many organisations, PIMs have been replaced by enterprise
information systems such as Microsoft Outlook. In many
organizations, PIMs have been
10. 6.2.1 From File Managers to Database Management Systems
A file manager is a program that allows users to work
with one file at a time.
A true database management system (DBMS) is a
program or system of programs that can manipulate
data in a large collection of files, cross-referencing
between files as needed. A database management
system can be used interactively, or it can be
controlled directly by other programs. With a
database management system, there’s no need to
store redundant information in every file. Instead a
key field is shared by all files that use the same data.
If redundant data changes, it need only be recorded
in one place.
11. 6.2.2 What Makes a Database
Relational?
To most users, a relational database program is one
that allows files to be related to each other so that
changes in one file are reflected in other files
automatically. To computer scientists, the term
relational database has a technical definition related
to the underlying structure of the data and the rules
specifying how that data can be manipulated.
The structure of a relational database is based on the
relational model—a mathematical model that combines
data in tables. Other kinds of database management
systems are based on different theoretical models, with
different technical advantages and disadvantages.
13. 6.3.1 Real-Time Computing
The earliest file management programs could only do batch
processing, which required users to accumulate
transactions and feed them into computers in large
batches. These batch systems weren’t able to provide the
kind of immediate feedback we expect today.
Today disk drives, inexpensive memory, and sophisticated
software have allowed interactive processing to replace
batch processing for most applications. Users can now
interact with data through terminals, viewing and
changing values in real time. Batch processing is still used
for printing periodic bills, invoices, and reports and for
making backup copies of data files. But for applications
that demand immediacy, such as airline reservations,
banking transactions, and the like, interactive, multi-user
database systems have taken over.
14. 6.3.2 Downsizing and
Decentralising
Until recently, most databases were housed in mainframe
computers. But for a growing number of organisations, the
traditional centralised database on a mainframe system is
no longer the norm.
Some companies use a client/server approach. Database
software in client desktop computers works with files
stored in central server databases on mainframes,
minicomputers, or desktop computers. Some companies
keep copies of all corporate data in an integrated data
warehouse, which give users more access to enterprise
data than the old-style centralised systems.
Other companies use distributed databases that use data
strewn out across networks on several different
computers. From the user’s point of view, the differences
between these approaches may not be apparent.
15. 6.3.2 Data Mining
Data mining is the discovery and extraction of hidden
predictive information from large databases using
statistical methods and artificial intelligence technology.
6.3.4 Object-Oriented Databases
Many computer scientists believe that the relational data model
may be supplanted in the next decade by an object-oriented
data model, and that most future databases will be object-
oriented databases rather than relational databases.
Instead of storing records in tables and hierarchies,
object-oriented databases store software objects that
contains procedures (or instructions) along with data.
Object-oriented databases often are used in conjunction
with object-oriented programming languages.
16. End Of Chapter SIX
Example of Pastel Accounting database program below
