CHAPTER 4 Relational Databases

Question 1

1. The relational data model portrays data as being stored in __________.
   a. hierarchies
   b. tables
   c. objects
   d. files

Answer 1

b. tables (Correct. The relational data model portrays data as being stored in a table or
relation format.)

Question 2

2. An employee database that consolidates payroll, personnel, and job skills master files is
referred to as
a. data integration. 
b. data sharing. 
c. data independence.

Answer 2

a. data integration. [Correct. Master files are combined into large “pools” of data that
many application programs access.]

Question 3

3. What is each row in a relational database table called?
   a. relation
   b. attribute
   c. anomaly
   d. tuple

Answer 3

d. tuple (Correct. A tuple is also called a row in a relational database.)

Question 4

4. The internal-level schema of a database system consists of an individual user’s view of
   portions of a database, also called a subschema.
   a. True
   b. False

Answer 4

b. False [Correct. The internal-level schema, a low-level view of the database, describes
how the data are stored and accessed, including record layouts, definitions, addresses,
and indexes.]

Question 5

5. Which of the following would managers most likely use to retrieve information about
sales during the month of October?
a. DML 
b. DSL 
c. DDL 
d. DQL

Answer 5

d. DQL (Correct. DQL—data query language—is used to retrieve information from a
database. )

Question 6

6. Which of the following attributes would most likely be a primary key?
   a. supplier name
   b. supplier number
   c. supplier Zip code
   d. supplier account balance

Answer 6

b. supplier number (Correct. A unique number can be assigned as a primary key for each
entity. )

Question 7

7. Which of the following is a software program that runs a database system?
   a. DQL
   b. DBMS
   c. DML
   d. DDL

Answer 7

b. DBMS (Correct. A DBMS—database management system—is a software program
that acts as an interface between a database and various application programs.)

Question 8

8. The constraint that all primary keys must have nonnull data values is referred to as which
of the following?
a. referential integrity rule 
b. entity integrity rule 
c. normalization rule 
d. relational data model rule

Answer 8

b. entity integrity rule (Correct. Every primary key in a relational table must have a
nonnull value.)

Question 9

9. The constraint that all foreign keys must have either null values or the value of a primary
   key in another table is referred to as which of the following?
   a. referential integrity rule
   b. entity integrity rule
   c. foreign key value rule
   d. null value rule

Answer 9

a. referential integrity rule (Correct. The referential integrity rule stipulates that foreign
keys must have values that correspond to the value of a primary key in another table or
be empty.)

Question 10

10. Which of the following is not a basic requirement of a relational database?
    a. Primary keys cannot be null.
    b. Every column in a row must be single valued.
    c. Foreign keys cannot be null.
    d. All non-key attributes in a table must describe a characteristic of the object identified by the primary key.

Answer 10

c. Foreign keys cannot be null. [Correct. Foreign keys, if not null, must have values
that correspond to the value of a primary key in another table. They link rows in one
table to rows in another table.]