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Exam 5: Advanced Data Modeling

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Question 21

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

A) True
B) False

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Question 22

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The completeness constraint can be partial or total.

A) True
B) False

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Question 23

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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.

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.

If one exists, a data modeler uses a as the primary key of the entity being modeled.

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

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

Nonoverlapping subtypes are subtypes that contain a(n) subset of the supertype entity set.

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

In the context of total completeness, in a(n) , every supertype occurrence is a member of at least one subtype.

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

In which two cases are composite primary keys particularly useful?

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

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

The preferred placement for a foreign key when working with a 1:1 relationship is to .

data refer to data whose values change over time and for which one must keep a history of the data changes.

Describe an entity cluster.

While using a surrogate key, one must ensure that the candidate key of the entity in question performs properly through the use of the " " and "not null" constraints.

Differentiate between specialization and generalization.

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