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Exam 5: Advanced Data Modeling

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Question 21

True/False

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

A) True
B) False

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Question 22

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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.

E) B) and C)
F) B) and D)

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Question 23

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_____ completeness means that not every supertype occurrence is a member of a subtype.

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

A(n) _____ 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 _____ is a primary key created by a database designer to simplify the identification of entity instances.

Explain the two criteria that help a designer in determining when to use subtypes and supertypes.

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.

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

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

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

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

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

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

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.

The purpose of an entity_____ is to simplify an entity-relationship diagram (ERD) and thus enhance its readability.

The completeness constraint can be partial or total.

Specialization is based on grouping _____ characteristics and relationships of the subtypes.

The most important characteristic of an entity is its _____ key, used to uniquely identify each entity instance.

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