Database Systems and Business Intelligence - Principles of Information Systems - page 183

League college provided an intruder with access to a database that stored students' private
information. 3 Such data breaches have become commonplace for businesses and organiza-
tions because many databases are now accessible from the Internet. Data quality and accuracy
also continue to be important issues for DBAs. A database error in the United Kingdom left
400,000 people without paychecks in March, 2007. 4
Databases and database management systems are becoming even more important to
businesses as they deal with increasing amounts of digital information. A report from IDC,
called “The Diverse and Exploding Digital Universe,” estimates the size of the digital universe
to be 281 exabytes, or 281 billion gigabytes. By 2011, there will be 1,800 exabytes of elec-
tronic data in existence, or 1.8 zettabytes. 5 If a tennis ball were one byte of information, a
zettabyte-sized ball would be around the size of one earth. IDC recommends that businesses
and organizations move now to create policies, tools, and standards to accommodate the
approaching tidal wave of digital data and information. 6

DATA MANAGEMENT

Without data and the ability to process it, an organization could not successfully complete
most business activities. It could not pay employees, send out bills, order new inventory, or
produce information to assist managers in decision making. Recall that data consists of raw
facts, such as employee numbers and sales figures. For data to be transformed into useful
information, it must first be organized in a meaningful way.

The Hierarchy of Data
Data is generally organized in a hierarchy that begins with the smallest piece of data used by
computers (a bit) and progresses through the hierarchy to a database. A bit (a binary digit)
represents a circuit that is either on or off. Bits can be organized into units called bytes . A
byte is typically eight bits. Each byte represents a character , which is the basic building
block of information. A character can be an uppercase letter (A, B, C… Z), lowercase letter
(a, b, c… z), numeric digit (0, 1, 2… 9), or special symbol (., !, [+], [-], /, …).
Characters can be combined to form a field. A field is typically a name, number, or
combination of characters that describes an aspect of a business object (such as an employee,
a location, or a truck) or activity (such as a sale). In addition to being entered into a database,
fields can be computed from other fields. Computed fields include the total, average, maxi-
mum, and minimum values. A collection of related data fields is a record . By combining
descriptions of the characteristics of an object or activity, a record can provide a complete
description of the object or activity. For instance, an employee record is a collection of fields
about one employee. One field includes the employee's name, another field contains the
address, and still others the phone number, pay rate, earnings made to date, and so forth. A
collection of related records is a file —for example, an employee file is a collection of all
company employee records. Likewise, an inventory file is a collection of all inventory records
for a particular company or organization. Some database software refers to files as tables.
At the highest level of this hierarchy is a database , a collection of integrated and related
files. Together, bits, characters, fields, records, files, and databases form the hierarchy of
data (see Figure 5.1). Characters are combined to make a field, fields are combined to make
a record, records are combined to make a file, and files are combined to make a database. A
database houses not only all these levels of data but also the relationships among them.

character
A basic building block of informa-
tion, consisting of uppercase letters,
lowercase letters, numeric digits, or
special symbols.

field
Typically a name, number, or com-
bination of characters that
describes an aspect of a business
object or activity.

record
A collection of related data fields.

file
A collection of related records.

hierarchy of data
Bits, characters, fields, records,
files, and databases.

Data Entities, Attributes, and Keys
Entities, attributes, and keys are important database concepts. An entity is a generalized
class of people, places, or things (objects) for which data is collected, stored, and maintained.
Examples of entities include employees, inventory, and customers. Most organizations
organize and store data as entities.

entity
A generalized class of people,
places, or things for which data is
collected, stored, and maintained.