1 © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 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 character istics 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 (c omputer) 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. 2 © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 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 (compu ter) 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 n eed 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 cont rol 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 summ arized 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 D BMS 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 perfo rms backup and data recovery procedures to ensure data safety. The DBMS promotes and enforces integrity rules to minimize data integrity problems. 3 © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 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 charact eristics, 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 shar ed, 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 s uch 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 w ay 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. 4 © 2023 Cengage. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. Improved data security . A DBMS provides a framework for better enforcement of data privacy and security po licies. 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 segm ents. 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 p robability 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 manipulati on (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 d ealing 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 advanta ges 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 interfac e with many different technologies and have a significant impact on a company’s resources and culture. The changes
