Table of Contents
Database System Applications
Databases are widely used. Here are some representative applications:
• Banking: For customer information, accounts, and loans, and banking
• Airlines: For reservations and schedule information. Airlines were among
the first to use databases in a geographically distributed manner—terminals
situated around the world accessed the central database system through
phone lines and other data networks.
• Universities: For student information, course registrations, and grades.
• Credit card transactions: For purchases on credit cards and generation of
• 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
financial instruments such as stocks and bonds.
• Sales: For customer, product, and purchase information.
• 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
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
indirectly—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 computers (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 collection, 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, database 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