Q&A Hero

Q: One practical advantage of a(n)___________ key is that because it has no intrinsic meaning, values for it can be generated by the DBMS to ensure that unique values are always provided.

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

Q: A weak-entity in a strong identifying relationship with a parent entity is normally used to represent a(n)________ that is represented in the data model as two separate entities.

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: Unique values can be better managed when they are________ , because the database can use internal routines to implement a counter-style attribute that automatically increments values with the addition of each new row.

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____________ 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. Redundantb. Duplicatedc. Time-variantd. Supertype

Q: 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 keyb. time-variant datac. design trapd. fan trap

Q: ______________data refer to data whose values change over time and for which one must keep a history of the data changes.a. Time-sensitiveb. Time-variantc. 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 optionalb. one side participates in another relationshipc. both sides are optionald. 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 entitiesb. create a bridge entityc. place the foreign key in one of the entitiesd. place the surrogate key in both entities

Q: ____________keys work with primary keys to properly implement relationships in the relational model.a. Foreignb. Compositec. Naturald. Surrogate

Q: Surrogate primary keys are especially helpful when there is no______________ key.a. primaryb. naturalc. foreignd. composite

Q: The "______________ " characteristic of a primary key states that the primary key should not have embedded semantic meaning.a. unique valuesb. nonintelligentc. preferably single-attributed. security-compliant

Q: According to the "preferably singleattribute" 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.

Q: The "_______________ " characteristic of a primary key states that the selected primary key must not be composed of anyattribute(s) that might be considered a violation.a. unique valuesb. nonintelligentc. preferably single-attributed. security-compliant

Q: 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 valuesb. nonintelligentc. 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. 0:1b. 1:1c. 1:Md. M:N

Q: A primary key's main function is to uniquely identify a(n)_______________ within a table.a. attributeb. entity instance or rowc. entity subtyped. natural key or identifier

Q: A ____________is a primary key created by a database designer to simplify the identification of entity instances.a. composite keyb. compound keyc. natural keyd. surrogate key

Q: If one exists, a data modeler uses a ___________as the primary key of the entity being modeled.a. foreign keyb. combination keyc. surrogate keyd. natural identifier

Q: A ________________key is a real-world, generally accepted identifier used to uniquely identify real-world objects.a. primaryb. naturalc. foreignd. surrogate

Q: The most important characteristic of an entity is its__________ key, used to uniquely identify each entity instance.a. primaryb. naturalc. foreignd. surrogate

Q: An entity cluster is formed by combining multiple interrelated entities into_______________ .a. a single abstract entity objectb. multiple abstract entity objectsc. a single entity objectd. multiple entity objects

Q: The purpose of a(n)___________ is to simplify an entity-relationship diagram (ERD) and thus enhance its readability.a. entity constraintb. entity clusterc. entity interfaced. entity discriminator

Q: ______________is the bottom-up process of identifying a higher-level, more generic entity supertype from lower-level entity subtypes.a. Specializationb. Generalizationc. Normalizationd. Total completeness

Q: In the context of total completeness, in a(n)________________ , every supertype occurrence is a member of at least one subtype.a. unique constraintb. disjoint constraintc. overlapping constraintd. foreign key constraint

Q: In the context of total completeness, in a(n)___________ , every supertype occurrence is a member of only one subtype.a. foreign key constraintb. nonunique constraintc. overlapping constraintd. disjoint constraint

Q: A partial completeness constraint is represented by_____________ .a. a dotted lineb. two dashed linesc. a single horizontal line under a circled. a double horizontal line over a circle

Q: A total completeness constraint is represented by _________.a. a smaller circle inside a bigger circleb. a rhombus inside a circlec. a double horizontal line under a circled. a single horizontal line above a circle

Q: Overlapping subtypes are subtypes that contain_______--- subsets of the supertype entity set.a. nullb. exclusivec. solitaryd. nonunique

Q: Nonoverlapping subtypes are subtypes that contain a(n)________ subset of the supertype entity set.a. entityb. subtypesc. uniqued. nonunique

Q: 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.

Q: 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.

Q: The default comparison condition for the subtype discriminator attribute is the___________ comparison.a. nonequalityb. less thanc. 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 discriminatorb. inheritance discriminatorc. specialization hierarchyd. entity supertype

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

Q: One important inheritance characteristic is that all entity subtypes inherit their_________ key attribute from their supertype.a. primaryb. naturalc. foreignd. surrogate

Q: The property of_____________ enables an entity subtype to inherit the attributes and relationships of the supertype.a. subtype discriminatorb. inheritancec. specialization hierarchyd. entity supertype

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

Q: Within a specialization hierarchy, every subtype can have ___________supertype(s) to which it is directly related.a. zerob. only onec. 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 discriminatorb. inheritancec. specialization hierarchyd. entity supertype

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

Q: 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

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

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.a. Trueb. False

Q: To model time-variant data, one must create a new entity in an M:N relationship with the original entity. a. True b. False

Q: The function of the primary key is to describe an entity. a. True b. False

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

Q: Generalization is based on grouping unique characteristics and relationships of the subtypes. a. True b. False

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

Q: The completeness constraint can be partial or total. a. True b. False

Q: Implementing nonoverlapping subtypes requires the use of one discriminator attribute for each subtype. a. True b. False

Q: Implementing overlapping subtypes requires the use of one discriminator attribute for each subtype. a. True b. False

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

Q: Disjoint subtypes are subtypes that contain nonunique subsets of the supertype entity set. a. True b. False

Q: An entity supertype can have disjoint or overlapping entity subtypes. a. True b. False

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

Q: 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

Q: Entity subtypes do not inherit the relationships in which the supertype entity participates. a. True b. False

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

Q: A subtype contains attributes that are common to all of its supertypes. a. True b. False

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

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

Q: The relationships depicted within the specialization hierarchy are sometimes described in terms of "isa" relationships. a. True b. False

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

Q: The entity supertype contains common characteristics, and the entity subtypes each contain their own unique characteristics. a. True b. False

Q: A(n)____________ relationship is also known as an identifying relationship.

Q: The concept of relationship strength is based on how the___________ of a related entity is defined.

Q: When indicating cardinality, the first value represents the_________ number of associated entities.

Q: A relationship_____________ is difficult to establish if only one side of the relationship is known.

Q: A(n)_________ attribute need not be physically stored within the database.