Silberschatz−Korth−Sudarshan:
Database System
Concepts, Fourth Edition
1. Introduction Text
12
© The McGraw−Hill
Companies, 2001
2 Chapter 1 Introduction
• Credit card transactions: For purchases on credit cards and generation of month-
ly statements.
• Telecommunication: For keeping records of calls made, generating monthly bills,
maintaining balances on prepaid calling cards, and storing information about
the communication networks.
• Finance: For storing information about holdings, sales, and purchases of finan-
cial instruments such as stocks and bonds.
• Sales:Forcustomer,product,andpurchaseinformation.
• Manufacturing: For management of supply chain and for tracking production
of items in factories, inventories of items in warehouses/stores, and orders for
items.
• Human resources: For information about employees, salaries, payroll taxes and
benefits, and for generation of paychecks.
As the list illustrates, databases form an essential part of almost all enterprises today.
Over the course of the last four decades of the twentieth century, use of databases
grew in all enterprises. In the early days, very few people interacted directly with
database systems, although without realizing it they interacted with databases in-
directly—through printed reports such as credit card statements, or through agents
such as bank tellers and airline reservation agents. Then automated teller machines
came along and let users interact directly with databases. Phone interfaces to com-
puters (interactive voice response systems) also allowed users to deal directly with
databases—a caller could dial a number, and press phone keys to enter information
or to select alternative options, to find flight arrival/departure times, for example, or
to register for courses in a university.
The internet revolution of the late 1990s sharply increased direct user access to
databases. Organizations converted many of their phone interfaces to databases into
Web interfaces, and made a variety of services and information available online. For
instance, when you access an online bookstore and browse a book or music collec-
tion, you are accessing data stored in a database. When you enter an order online,
your order is stored in a database. When you access a bank Web site and retrieve
your bank balance and transaction information, the information is retrieved from the
bank’s database system. When you access a Web site, information about you may be
retrieved from a database, to select which advertisements should be shown to you.
Furthermore, data about your Web accesses may be stored in a database.
Thus, although user interfaces hide details of access to a database, and most people
are not even aware they are dealing with a database, accessing databases forms an
essential part of almost everyone’s life today.
The importance of database systems can be judged in another way—today, data-
base system vendors like Oracle are among the largest software companies in the
world, and database systems form an important part of the product line of more
diversified companies like Microsoft and IBM.
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