Solution and Answer Guide
CORONEL AND MORRIS, DATABASE SYSTEMS: DESIGN, IMPLEMENTATION AND MANAGEMENT,
©2023, 9780357673034;
CHAPTER 1: DATABASE SYSTEMS
TABLE OF CONTENTS
Answers to Review Questions…….................................…………………………………………….1
Answers to Problems ...............................................................................................................9
ANSWERS TO REVIEW QUESTIONS
1. Define each of the following terms:
Answer:
a. data
Raw facts from which the required information is derived. Data have little meaning unless
they are grouped in a logical manner.
b. field
A character or a group of characters (numeric or alphanumeric) that describes a specific
characteristic. A field may define a telephone number, a date, or other specific characteristics
that the end user wants to keep track of.
c. record
A logically connected set of one or more fields that describes a person, place, event, or thing.
For example, a CUSTOMER record may be composed of the fields CUST_NUMBER,
CUST_LNAME, CUST_FNAME, CUST_INITIAL, CUST_ADDRESS, CUST_CITY,
CUST_STATE, CUST_ZIPCODE, CUST_AREACODE, and CUST_PHONE.
d. file
Historically, a collection of file folders, properly tagged and kept in a filing cabinet. Although
such manual files still exist, we more commonly think of a (computer) file as a collection of
related records that contain information of interest to the end user. For example, a sales
organization is likely to keep a file containing customer data. Keep in mind that the phrase
related records reflects a relationship based on function. For example, customer data are
kept in a file named CUSTOMER. The records in this customer file are related by the fact that
they all pertain to customers. Similarly, a file named PRODUCT would contain records that
describe products—the records in this file are all related by the fact that they all pertain to
products. You would not expect to find customer data in a product file, or vice versa.
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, NOTE
Field, record, and file are computer terms, created to help describe how data
are stored in secondary memory. Emphasize that computer file data storage
does not match the human perception of such data storage.
2. What is data redundancy, and which characteristics of the file system can lead to it?
Answer: Data redundancy exists when unnecessarily duplicated data are found in the
database. For example, a customer’s telephone number may be found in the customer file, in
the sales agent file, and in the invoice file. Data redundancy is symptomatic of a (computer)
file system, given its inability to represent and manage data relationships. Data redundancy
may also be the result of poorly designed databases that allow the same data to be kept in
different locations. (Here's another opportunity to emphasize the need for good database
design!)
3. What is data independence, and why is it lacking in file systems?
Answer: Data independence is a condition in which the programs that access data are not
dependent on the data storage characteristics of the data. Systems that lack data
independence are said to exhibit data dependence. File systems exhibit data dependence
because file access is dependent on a file’s data characteristics. Therefore, any time the file
data characteristics are changed, the programs that access the data within those files must
be modified.
Data independence exists when changes in the data characteristics don’t require changes in
the programs that access those data. File systems lack data independence because all data
access programs are subject to change when any of the file system’s data storage
characteristics—such as changing a data type—change.
4. What is a DBMS, and what are its functions?
Answer: A DBMS is best described as a collection of programs that manage the database
structure and that control shared access to the data in the database. Current DBMSs also
store the relationships between the database components; they also take care of defining the
required access paths to those components. The functions of a current-generation DBMS
may be summarized as follows:
The DBMS stores the definitions of data and their relationships (metadata) in a data
dictionary; any changes made are automatically recorded in the data dictionary.
The DBMS creates the complex structures required for data storage.
The DBMS transforms entered data to conform to the data structures in the previous
item.
The DBMS creates a security system and enforces security within that system.
The DBMS creates complex structures that allow multiple-user access to the data.
The DBMS performs backup and data recovery procedures to ensure data safety.
The DBMS promotes and enforces integrity rules to minimize data integrity problems.
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, The DBMS provides access to the data via utility programs and from programming
languages interfaces.
The DBMS provides end-user access to data within a computer network
environment.
5. What is structural independence, and why is it important?
Answer: Structural independence exists when data access programs are not subject to change
when the file’s structural characteristics, such as the number or order of the columns in a table,
change. Structural independence is important because it substantially decreases programming
effort and program maintenance costs.
6. Explain the differences among data, information, and a database.
Answer: Data are raw facts. Information is processed data to reveal the meaning behind the
facts. Let’s summarize some key points:
Data constitute the building blocks of information.
Information is produced by processing data.
Information is used to reveal the meaning of data.
Good, relevant, and timely information is the key to good decision making.
Good decision making is the key to organizational survival in a global environment.
A database is a computer structure for storing data in a shared, integrated fashion so that the
data can be transformed into information as needed.
7. What is the role of a DBMS, and what are its advantages? What are its disadvantages?
Answer: A database management system (DBMS) is a collection of programs that
manages the database structure and controls access to the data stored in the database.
Figure 1.4 (shown in the text) illustrates that the DBMS serves as the intermediary between
the user and the database. The DBMS receives all application requests and translates them
into the complex operations required to fulfill those requests. The DBMS hides much of the
database’s internal complexity from the application programs and users. The application
program might be written by a programmer using a programming language such as COBOL,
Visual Basic, or C++, or it might be created through a DBMS utility program.
Having a DBMS between the end user’s applications and the database offers some important
advantages. First, the DBMS enables the data in the database to be shared among multiple
applications or users. Second, the DBMS integrates the many different users’ views of the
data into a single all-encompassing data repository.
Because data are the crucial raw material from which information is derived, you must have a
good way of managing such data. As you will discover in this book, the DBMS helps make
data management more efficient and effective. In particular, a DBMS provides advantages
such as:
Improved data sharing. The DBMS helps create an environment in which end users
have better access to more and better-managed data. Such access makes it possible
for end users to respond quickly to changes in their environment.
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, Improved data security. A DBMS provides a framework for better enforcement of data
privacy and security policies.
Better data integration. Wider access to well-managed data promotes an integrated
view of the organization’s operations and a clearer view of the big picture. It becomes
much easier to see how actions in one segment of the company affect other
segments.
Minimized data inconsistency. Data inconsistency exists when different versions of
the same data appear in different places. For example, data inconsistency exists
when a company’s sales department stores a sales representative’s name as “Bill
Brown” and the company’s personnel department stores that same person’s name as
“William G. Brown” or when the company’s regional sales office shows the price of
product “X” as $45.95 and its national sales office shows the same product’s price as
$43.95. The probability of data inconsistency is greatly reduced in a properly
designed database.
Improved data access. The DBMS makes it possible to produce quick answers to ad
hoc queries. From a database perspective, a query is a specific request for data
manipulation (e.g., to read or update the data) issued to the DBMS. Simply put, a
query is a question and an ad hoc query is a spur-of-the-moment question. The
DBMS sends back an answer (called the query result set) to the application. For
example, end users, when dealing with large amounts of sales data, might want quick
answers to questions (ad hoc queries) such as:
What was the dollar volume of sales by product during the past six months?
What is the sales bonus figure for each of our salespeople during the past
three months?
How many of our customers have credit balances of $3,000 or more?
Improved decision making. Better-managed data and improved data access make it
possible to generate better-quality information, on which better decisions are based.
Increased end-user productivity. The availability of data, combined with the tools that
transform data into usable information, empowers end users to make quick, informed
decisions that can make the difference between success and failure in the global
economy.
The advantages of using a DBMS are not limited to the few just listed. In fact, you will
discover many more advantages as you learn more about the technical details of databases
and their proper design.
Although the database system yields considerable advantages over previous data
management approaches, database systems do carry significant disadvantages. For
example:
Increased costs. Database systems require sophisticated hardware and software and
highly skilled personnel. The cost of maintaining the hardware, software, and
personnel required to operate and manage a database system can be substantial.
Training, licensing, and regulation compliance costs are often overlooked when
database systems are implemented.
Management complexity. Database systems interface with many different technologies
and have a significant impact on a company’s resources and culture. The changes
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