Chapter 5

Question 1

According to the “preferably single-attribute” characteristic of a primary key, the primary key:

a) must be composed of attributes that are free from security risks or violations.
b) must be able to guarantee unique attribute values.
c) should have the minimum number of attributes possible.
d) should have embedded semantic meaning associated with each attribute.

Answer 1

c) should have the minimum number of attributes possible.

Question 2

The function of the primary key is to describe an entity.

a) true
b) false

Answer 2

a) true

Question 3

Implementing nonoverlapping subtypes requires the use of one discriminator attribute for each subtype.

a) true
b) false

Answer 3

b) false

Question 4

Some designs use redundant relationships as a way to simplify the design.

a) true
b) false

Answer 4

a) true

Question 5

Within a specialization hierarchy, every subtype can have _____ supertype(s) to which it is directly related.

a) zero
b) only one
c) many
d) one or many

Answer 5

b) only one

Question 6

One important inheritance characteristic is that all entity subtypes inherit their _____ key attribute from their supertype.

a) primary
b) natural
c) surrogate
d) foreign

Answer 6

a) primary

Question 7

Entity supertypes and subtypes are organized in a specialization hierarchy.

a) true
b) false

Answer 7

a) true

Question 8

Overlapping subtypes are subtypes that contain _____ subsets of the supertype entity set.

a) exclusive
b) null
c) solitary
d) nonunique

Answer 8

d) nonunique

Question 9

The relationships depicted within the specialization hierarchy are sometimes described in terms of “is-a” relationships.

a) true
b) false

Answer 9

a) true

Question 10

In specialization hierarchies with multiple levels of supertype and subtypes, a lower-level subtype can inherit only a few of the attributes and relationships from its upper-level supertypes.

a) true
b) false

Answer 10

b) false

Question 11

A specialization hierarchy can have _____ level(s) of supertype/subtype relationships.

a) many
b) zero
c) only one
d) one or many

Answer 11

a) many

Question 12

_____ is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes.

a) Generalization
b) Total completeness
c) Normalization
d) Specialization

Answer 12

a) Generalization

Question 13

The completeness constraint can be partial or total.

a) true
b) false

Answer 13

a) true

Question 14

The “_____” characteristic of a primary key states that the selected primary key must not be composed of any attribute(s) that might be considered a violation.

a) nonintelligent
b) unique values
c) preferably single-attribute
d) security-compliant

Answer 14

b) unique values

Question 15

A _____ key is a real-world, generally accepted identifier used to uniquely identify real-world objects.

a) foreign
b) surrogate
c) natural
d) primary

Answer 15

c) natural

Question 16

Specialization is the top-down process of identifying lower-level, more specific entity subtypes from a higher-level entity supertype.

a) true
b) false

Answer 16

a) true

Question 17

At the implementation level, the supertype and its subtype(s) depicted in the specialization hierarchy maintain a 1:1 relationship.

a) true
b) false

Answer 17

a) true

Question 18

The default comparison condition for the subtype discriminator attribute is the _____ comparison.

a) less than
b) equality
c) greater than
d) nonequality

Answer 18

b) equality

Question 19

Which of the following is a specialization hierarchy overlapping constraint scenario in case of partial completeness?

a) Supertype has optional subtypes.
b) Subtype discriminators cannot be null.
c) Subtype sets are unique.
d) Subtype does not have a supertype.

Answer 19

a) Supertype has optional subtypes.

Question 20

When selecting a foreign key placement for a 1:1 relationship, place the PK of the entity on the mandatory side in the entity on the optional side as a FK, and make the FK mandatory when _____.

a) both sides are mandatory
b) both sides are optional
c) one side participates in another relationship
d) one side is mandatory and the other side is optional

Answer 20

d) one side is mandatory and the other side is optional