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The default comparison condition for the subtype discriminator attribute is the _____ comparison.


A) nonequality
B) less than
C) greater than
D) equality

E) None of the above
F) C) and D)

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An entity supertype can have disjoint or overlapping entity subtypes.

A) True
B) False

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Differentiate between specialization and generalization.

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Specialization is the top-down process o...

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

A) True
B) False

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A _____ key is a real-world, generally accepted identifier used to uniquely identify real-world objects.


A) primary
B) natural
C) foreign
D) surrogate

E) A) and C)
F) None of the above

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

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time-variant

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

A) True
B) False

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False

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

E) B) and C)
F) A) and C)

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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

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

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B

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

E) A) and C)
F) C) and D)

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

A) True
B) False

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A total completeness constraint is represented by a _____.


A) smaller circle inside a bigger circle
B) rhombus inside a circle
C) double horizontal line under a circle
D) single horizontal line above a circle

E) A) and B)
F) A) and C)

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

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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

E) B) and D)
F) None of the above

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_____ keys work with primary keys to properly implement relationships in the relational model.

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

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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.

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In which two cases are composite primary keys particularly useful?

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Composite primary keys are particularly ...

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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

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

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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.

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

Correct Answer

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