DATABASE MANAGEMENT CHAPTER 05 - FOR FINAL EXAM

If one exists, a data modeler uses a __________ as the primary key of the entity being modeled. a. foreign key b. combination key c. surrogate key d. natural identifier

d. natural identifier

Overlapping subtypes are subtypes that contain __________ subsets of the supertype entity set. a. null b. exclusive c. solitary d. nonunique

d. nonunique

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

d. security-compliant

A __________ is a primary key created by a database designer to simplify the identification of entity instances. a. composite key b. compound key c. natural key d. surrogate key

d. surrogate key

A subtype contains attributes that are common to all of its supertypes. T/F

False

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. T/F

False

Overlapping subtypes are subtypes that contain a unique subset of the supertype entity set. T/F

False

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

False

The property of a subtype discriminator enables an entity supertype to inherit the attributes and relationships of the subtype. T/F

False

Within a specialization hierarchy, a supertype can exist only within the context of a subtype. T/F

False

__________ relationships occur when there are multiple relationship paths between related entities. a. Redundant b. Duplicated c. Time-variant d. Supertype

a. Redundant

Which of the following is a specialization hierarchy disjoint constraint scenario in case of partial completeness? a. Subtype discriminator can be null. b. Subtype discriminator cannot be null. c. Each supertype occurrence is a member of only one subtype. d. Each supertype occurrence is a member of at least one subtype.

a. Subtype discriminator can be null.

An entity cluster is formed by combining multiple interrelated entities into __________. a. a single abstract entity object b. multiple abstract entity objects c. a single entity object d. multiple entity objects

a. a single abstract entity object

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

a. one side is mandatory and the other side is optional

The __________ depicts the arrangement of higher-level entity supertypes (parent entities) and lower-level entity subtypes (child entities). a. subtype discriminator b. inheritance c. specialization hierarchy d. entity supertype

c. specialization hierarchy

Nonoverlapping subtypes are subtypes that contain a(n) __________ subset of the supertype entity set. a. entity b. subtypes c. unique d. nonunique

c. unique

An entity supertype can have disjoint or overlapping entity subtypes. T/F

True

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

True

The completeness constraint can be partial or total. T/F

True

The relationships depicted within the specialization hierarchy are sometimes described in terms of "is-a" relationships. T/F

True

__________ keys work with primary keys to properly implement relationships in the relational model. a. Foreign b. Composite c. Natural d. Surrogate

a. Foreign

A __________ key is a real-world, generally accepted identifier used to uniquely identify real-world objects. a. primary b. natural c. foreign d. surrogate

b. natural

Surrogate primary keys are especially helpful when there is no __________ key. a. primary b. natural c. foreign d. composite

b. natural

The "__________" characteristic of a primary key states that the primary key should not have embedded semantic meaning. a. unique values b. nonintelligent c. preferably single-attribute d. security-compliant

b. nonintelligent

The default comparison condition for the subtype discriminator attribute is the __________ comparison. a. nonequality b. less than c. greater than d. equality

d. equality

Disjoint subtypes are subtypes that contain nonunique subsets of the supertype entity set. T/F

False

Entity subtypes do not inherit the relationships in which the supertype entity participates. T/F

False

Generalization is based on grouping unique characteristics and relationships of the subtypes. T/F

False

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

False

To model time-variant data, one must create a new entity in an M:N relationship with the original entity. T/F

False

A design trap occurs when a relationship is improperly or incompletely identified and is therefore represented in a way that is not consistent with the real world. T/F

True

An entity cluster is a "virtual" entity type used to represent multiple entities and relationships in the ERD. T/F

True

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

True

Entity supertypes and subtypes are organized in a specialization hierarchy. T/F

True

Implementing overlapping subtypes requires the use of one discriminator attribute for each subtype. T/F

True

One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their supertype. T/F

True

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

True

The entity supertype contains common characteristics, and the entity subtypes each contain their own unique characteristics. T/F

True

One important inheritance characteristic is that all entity subtypes inherit their __________ key attribute from their supertype. a. primary b. natural c. foreign d. surrogate

a. primary

The most important characteristic of an entity is its __________ key, used to uniquely identify each entity instance. a. primary b. natural c. foreign d. surrogate

a. primary

A(n) __________ is the attribute in the supertype entity that determines to which entity subtype each supertype occurrence is related. a. subtype discriminator b. inheritance discriminator c. specialization hierarchy d. entity supertype

a. subtype discriminator

The "__________" characteristic of a primary key states that the primary key must uniquely identify each entity instance, must be able to guarantee unique values, and must not contain nulls. a. unique values b. nonintelligent c. preferably single-attribute d. security-complaint

a. unique values

At the implementation level, the supertype and its subtype(s) depicted in a specialization hierarchy maintain a(n) __________ relationship. a. self-referencing b. 1:1 c. 1:M d. M:N

b. 1:1

__________ is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes. a. Specialization b. Generalization c. Normalization d. Total completeness

b. Generalization

Which of the following is a specialization hierarchy overlapping constraint scenario in case of partial completeness? a. Subtype sets are unique. b. Supertype has optional subtypes. c. Subtype discriminators cannot be null. d. Subtype does not have a supertype.

b. Supertype has optional subtypes.

__________ data refer to data whose values change over time and for which one must keep a history of the data changes. a. Time-sensitive b. Time-variant c. Historical d. Change-based

b. Time-variant

The extended entity relationship model (EERM) is sometimes referred to as the __________. a. enclosed entity relationship model b. enhanced entity relationship model c. entity clustering relationship model d. extended entity relationship diagram

b. enhanced entity relationship model

The purpose of a(n) __________ is to simplify an entity-relationship diagram (ERD) and thus enhance its readability. a. entity constraint b. entity cluster c. entity interface d. entity discriminator

b. entity cluster

A primary key's main function is to uniquely identify a(n) __________ within a table. a. attribute b. entity instance or row c. entity subtype d. natural key or identifier

b. entity instance or row

The property of __________ enables an entity subtype to inherit the attributes and relationships of the supertype. a. subtype discriminator b. inheritance c. specialization hierarchy d. entity supertype

b. inheritance

Within a specialization hierarchy, every subtype can have __________ supertype(s) to which it is directly related. a. zero b. only one c. one or many d. many

b. only one

According to the "preferably single-attribute" characteristic of a primary key, the primary key: a. must be able to guarantee unique attribute values. b. should have the minimum number of attributes possible. c. should have embedded semantic meaning associated with each attribute. d. must be composed of attributes that are free from security risks or violations.

b. should have the minimum number of attributes possible.

A total completeness constraint is represented by __________. a. a smaller circle inside a bigger circle b. a rhombus inside a circle c. a double horizontal line under a circle d. a single horizontal line above a circle

c. a double horizontal line under a circle

A partial completeness constraint is represented by __________. a. a dotted line b. two dashed lines c. a single horizontal line under a circle d. a double horizontal line over a circle

c. a single horizontal line under a circle

In the context of total completeness, in a(n) __________, every supertype occurrence is a member of at least one subtype. a. unique constraint b. disjoint constraint c. overlapping constraint d. foreign key constraint

c. overlapping constraint

The preferred placement for a foreign key when working with a 1:1 relationship is to __________. a. use the same primary key for both entities b. create a bridge entity c. place the foreign key in one of the entities d. place the surrogate key in both entities

c. place the foreign key in one of the entities

__________ is a generic entity type that is related to one or more entity subtypes. a. A subtype discriminator b. Inheritance c. A specialization hierarchy d. An entity supertype

d. An entity supertype

Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed only once in the __________ relationship. a. 0:1 b. 1:1 c. 1:M d. M:N

d. M:N

In the context of total completeness, in a(n) __________, every supertype occurrence is a member of only one subtype. a. foreign key constraint b. nonunique constraint c. overlapping constraint d. disjoint constraint

d. disjoint constraint

A __________ occurs when there is one entity in two 1:M relationships to other entities, thus producing an association among the other entities that is not expressed in the model. a. surrogate primary key b. time-variant data c. design trap d. fan trap

d. fan trap

A specialization hierarchy can have __________ level(s) of supertype/subtype relationships. a. zero b. only one c. one or many d. many

d. many