Q&A Hero

Q: In a real-world environment, we must strike a balance between design integrity and ____.a. robustnessb. flexibility c. uniquenessd. ease of use

Q: In what two cases are composite primary keys particularly useful?

Q: Explain the "no change over time" characteristic of a good primary key.

Q: What is an entity cluster?

Q: Describe specialization and generalization.

Q: What do specialization hierarchies do?

Q: The main concern with redundant relationships is that they remain ____________________ across the model.

Q: The most common design trap is known as a(n) ____________________.

Q: From a data modeling point of view, ____________________ data refer to data whose values change over time and for which you must keep a history of the data changes.

Q: If you use a surrogate key, you must ensure that the candidate key of the entity in question performs properly through the use of the "____________________" and "not null" constraints.

Q: Composite keys are useful as identifiers of weak entities, where the weak entity has a strong ____________________ relationship with the parent entity.

Q: Composite primary keys are particularly useful as identifiers of composite entities, where each primary key combination is allowed ____________________ in the M:N relationship.

Q: Usually, a data modeler uses a natural identifier as the ____________________ of the entity being modeled, assuming that the entity has a natural identifier.

Q: An entity cluster is considered "virtual" or "____________________" in the sense that it is not actually an entity in the final ERD.

Q: Specialization is based on grouping ____________________ characteristics and relationships of the subtypes.

Q: ____________________ completeness means that every supertype occurrence must be a member of at least one subtype.

Q: ____________________ completeness means that not every supertype occurrence is a member of a subtype.

Q: The ____________________ constraint specifies whether each entity supertype occurrence must also be a member of at least one subtype.

Q: Subtypes that contain nonunique subsets of the supertype entity set are known as ____________________ subtypes.

Q: Disjoint subtypes are also known as ____________________ subtypes.

Q: The ____________________ is the result of adding more semantic constructs to the original entity relationship (ER) model.

Q: ____ relationships occur when there are multiple relationship paths between related entities.a. Redundant b. Duplicated c. Time-variantd. Supertype

Q: A ____ occurs when you have 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 keys b. time-variant data c. design trapd. fan trap

Q: ____ data refer to data whose values change over time and for which you must keep a history of the data changes.a. Time-sensitive b. Time-variant c. Historicald. Change-based

Q: 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

Q: 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 a foreign key in one of the entities d. place a foreign key in both entities

Q: ____ keys work with primary keys to properly implement relationships in the relational model.a. Foreign b. Composite c. Naturald. Surrogate

Q: Surrogate primary keys are especially helpful when there is no ____ key.a. primary b. natural c. foreignd. composite

Q: The "____" characteristic of a primary key states the following:The PK should not have embedded semantic meaning. An attribute with embedded semantic meaning is probably better used as a descriptive characteristic of the entity rather than as an identifier.a. unique values b. nonintelligent c. preferably single-attributed. security compliant

Q: The "____" characteristic of a primary key states the following:The selected primary key must not be composed of any attribute(s) that might be considered a security risk or violation. For example, using a Social Security number as a PK in an EMPLOYEE table is not a good idea.a. unique values b. nonintelligent c. preferably single-attributed. security-compliant

Q: The "____" characteristic of a primary key states the following:The PK must uniquely identify each entity instance. A primary key must be able to guarantee unique values. It cannot contain nulls.a. unique values b. nonintelligent c. preferably single-attributed. security complaint

Q: 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:Md. M:N

Q: The primary key's main function is to uniquely identify a(n) ____ within a table.a. attribute b. entity instance or row c. entity subtyped. natural identifier

Q: 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 keyd. natural identifier

Q: A ____ key is a real-world, generally accepted identifier used to uniquely identify real-world objects.a. primary b. natural c. foreignd. surrogate

Q: The most important characteristic of an entity is its ____ key, used to uniquely identify each entity instance.a. primary b. natural c. foreignd. surrogate

Q: 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 objectd. multiple entity objects

Q: ____ is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes.a. Specialization b. Generalization c. Partial completenessd. Total completeness

Q: Partial completeness is symbolized by ____.a. a dotted line b. two dashed lines c. a circle over a single lined. a circle over a double line

Q: Overlapping subtypes are subtypes that contain ____ subsets of the supertype entity set.a. entity b. subtypes c. uniqued. nonunique

Q: Non-overlapping subtypes are subtypes that contain a(n) ____ subset of the supertype entity set.a. entity b. subtypes c. uniqued. nonunique

Q: The default comparison condition for the subtype discriminator attribute is the ____ comparison.a. not equality b. less than c. greater thand. equality

Q: 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 hierarchyd. entity supertype

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

Q: One important inheritance characteristic is that all entity subtypes inherit their ____ key attribute from their supertype.a. primary b. natural c. foreignd. surrogate

Q: The property of ____ enables an entity subtype to inherit the attributes and relationships of the supertype.a. subtype discriminator b. inheritance c. specialization hierarchyd. entity supertype

Q: A specialization hierarchy can have ____ level(s) of supertype/subtype relationships.a. zerob. only one c. one or manyd. many

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

Q: 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 hierarchyd. entity supertype

Q: ____ is a generic entity type that is related to one or more entity subtypes.a. A subtype discriminatorb. Inheritance c. A specialization hierarchyd. An entity supertype

Q: The extended entity relationship model (EERM) is sometimes referred to as the ____.a. entity relationship model b. enhanced entity relationship model c. entity clustering relationship modeld. extended entity relationship diagram

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

Q: 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.

Q: To model time-variant data, you must create a new entity in a M:N relationship with the original entity.

Q: An entity cluster is a "virtual" entity type used to represent multiple entities and relationships in the ERD.

Q: Generalization is based on grouping unique characteristics and relationships of the subtypes.

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

Q: The completeness constraint can be partial or total.

Q: Implementing non-overlapping subtypes requires the use of one discriminator attribute for each subtype.

Q: Overlapping subtypes are subtypes that contain a unique subset of the supertype entity set.

Q: Disjoint subtypes are subtypes that contain nonunique subsets of the supertype entity set.

Q: An entity supertype can have disjoint or overlapping entity subtypes.

Q: The property of subtype discriminator enables an entity supertype to inherit the attributes and relationships of the subtype.

Q: In specialization hierarchies with multiple levels of supertype/subtypes, a lower-level supertype inherits all of the attributes and relationships from all of its upper-level subtypes.

Q: Entity subtypes do not inherit the relationships in which the supertype entity participates.

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

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

Q: Within a specialization hierarchy, a supertype can exist only within the context of a subtype.

Q: The relationships depicted within the specialization hierarchy are sometimes described in terms of "is-a" relationships.

Q: Entity supertypes and subtypes are organized in a specialization hierarchy.

Q: The entity supertype contains the common characteristics and the entity subtypes contain the unique characteristics of each entity subtype.

Q: What is a ternary relationship? Provide some example business rules that specify the need for a ternary or higher-order relationship.

Q: What is a weak relationship? Provide an example.

Q: Explain multivalued attributes, and provide an example. How are multivalued attributes indicated in the Chen model? How are they indicated in the Crow's Foot model?

Q: Explain single-valued attributes and provide an example. Is an attribute that is single-valued always simple? Why or why not? Use an example to illustrate your point.

Q: Explain the difference between simple and composite attributes. Provide at least one example of each.

Q: ____________________ not only helps you stay on track during the design process, it also enables you and your coworkers to pick up the design thread when the time comes to modify the design.

Q: Identifying the attributes of the entities helps you better understand the ____________________ among entities.

Q: A(n) ____________________ process is based on repetition of processes and procedures.

Q: A relationship ____________________ indicates the number of entities or participants associated with a relationship.