Deck 5: Advanced Data Modeling
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Deck 5: Advanced Data Modeling
1
The completeness constraint can be partial or total.
True
2
The entity supertype contains the common characteristics and the entity subtypes contain the unique characteristics of each entity subtype.
True
3
At the implementation level,the supertype and its subtype(s)depicted in the specialization hierarchy maintain a 1:1 relationship.
True
4
Implementing non-overlapping subtypes requires the use of one discriminator attribute for each subtype.
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5
An entity cluster is a "virtual" entity type used to represent multiple entities and relationships in the ERD.
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6
The relationships depicted within the specialization hierarchy are sometimes described in terms of "is-a" relationships.
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7
To model time-variant data,you must create a new entity in a M:N relationship with the original entity.
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8
Some designs use redundant relationships as a way to simplify the design.
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9
The property of subtype discriminator enables an entity supertype to inherit the attributes and relationships of the subtype.
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10
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.
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11
Overlapping subtypes are subtypes that contain a unique subset of the supertype entity set.
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12
One important inheritance characteristic is that all entity subtypes inherit their primary key attribute from their supertype.
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13
Disjoint subtypes are subtypes that contain nonunique subsets of the supertype entity set.
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14
Generalization is based on grouping unique characteristics and relationships of the subtypes.
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15
An entity supertype can have disjoint or overlapping entity subtypes.
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16
Entity supertypes and subtypes are organized in a specialization hierarchy.
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17
Entity subtypes do not inherit the relationships in which the supertype entity participates.
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18
Specialization is the top-down process of identifying lower-level,more specific entity subtypes from a higher-level entity supertype.
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19
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.
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20
Within a specialization hierarchy,a supertype can exist only within the context of a subtype.
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21
____ 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 completeness
D) Total completeness
A) Specialization
B) Generalization
C) Partial completeness
D) Total completeness
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22
Partial completeness is symbolized by ____.
A) a dotted line
B) two dashed lines
C) a circle over a single line
D) a circle over a double line
A) a dotted line
B) two dashed lines
C) a circle over a single line
D) a circle over a double line
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23
The primary key's main function is to uniquely identify a(n)____ within a table.
A) attribute
B) entity instance or row
C) entity subtype
D) natural identifier
A) attribute
B) entity instance or row
C) entity subtype
D) natural identifier
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24
____ is a generic entity type that is related to one or more entity subtypes.
A) A subtype discriminator
B) Inheritance
C) A specialization hierarchy
D) An entity supertype
A) A subtype discriminator
B) Inheritance
C) A specialization hierarchy
D) An entity supertype
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25
An entity cluster is formed by combining multiple interrelated entities into ____.
A) a single abstract entity object
B) multiple abstract entity object
C) a single entity object
D) multiple entity objects
A) a single abstract entity object
B) multiple abstract entity object
C) a single entity object
D) multiple entity objects
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26
Overlapping subtypes are subtypes that contain ____ subsets of the supertype entity set.
A) entity
B) subtypes
C) unique
D) nonunique
A) entity
B) subtypes
C) unique
D) nonunique
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27
Non-overlapping subtypes are subtypes that contain a(n)____ subset of the supertype entity set.
A) entity
B) subtypes
C) unique
D) nonunique
A) entity
B) subtypes
C) unique
D) nonunique
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28
The default comparison condition for the subtype discriminator attribute is the ____ comparison.
A) not equality
B) less than
C) greater than
D) equality
A) not equality
B) less than
C) greater than
D) equality
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29
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
A) subtype discriminator
B) inheritance
C) specialization hierarchy
D) entity supertype
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30
One important inheritance characteristic is that all entity subtypes inherit their ____ key attribute from their supertype.
A) primary
B) natural
C) foreign
D) surrogate
A) primary
B) natural
C) foreign
D) surrogate
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31
A specialization hierarchy can have ____ level(s)of supertype/subtype relationships.
A) zero
B) only one
C) one or many
D) many
A) zero
B) only one
C) one or many
D) many
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32
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 model
D) extended entity relationship diagram
A) entity relationship model
B) enhanced entity relationship model
C) entity clustering relationship model
D) extended entity relationship diagram
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33
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 key
D) natural identifier
A) foreign key
B) combination key
C) surrogate key
D) natural identifier
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34
Within a specialization hierarchy,every subtype can have ____ supertype(s)to which it is directly related.
A) zero
B) only one
C) one or many
D) many
A) zero
B) only one
C) one or many
D) many
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35
The most important characteristic of an entity is its ____ key,used to uniquely identify each entity instance.
A) primary
B) natural
C) foreign
D) surrogate
A) primary
B) natural
C) foreign
D) surrogate
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36
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
A) subtype discriminator
B) inheritance discriminator
C) specialization hierarchy
D) entity supertype
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37
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:M
D) M:N
A) 0:1
B) 1:1
C) 1:M
D) M:N
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38
A ____ key is a real-world,generally accepted identifier used to uniquely identify real-world objects.
A) primary
B) natural
C) foreign
D) surrogate
A) primary
B) natural
C) foreign
D) surrogate
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39
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 hierarchy
D) entity supertype
A) subtype discriminator
B) inheritance
C) specialization hierarchy
D) entity supertype
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40
At the implementation level,the supertype and its subtype(s)depicted in the specialization hierarchy maintain a ____ relationship.
A) self-referencing
B) 1:1
C) 1:M
D) M:N
A) self-referencing
B) 1:1
C) 1:M
D) M:N
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41
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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42
____ 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) Historical
D) Change-based
A) Time-sensitive
B) Time-variant
C) Historical
D) Change-based
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43
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
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
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44
Surrogate primary keys are especially helpful when there is no ____ key.
A) primary
B) natural
C) foreign
D) composite
A) primary
B) natural
C) foreign
D) composite
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45
____ keys work with primary keys to properly implement relationships in the relational model.
A) Foreign
B) Composite
C) Natural
D) Surrogate
A) Foreign
B) Composite
C) Natural
D) Surrogate
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46
Specialization is based on grouping ____________________ characteristics and relationships of the subtypes.
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47
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-attribute
D) security complaint
A) unique values
B) nonintelligent
C) preferably single-attribute
D) security complaint
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48
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-attribute
D) security compliant
A) unique values
B) nonintelligent
C) preferably single-attribute
D) security compliant
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49
The ____________________ constraint specifies whether each entity supertype occurrence must also be a member of at least one subtype.
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50
Usually,a data modeler uses a natural identifier as the ____________________ of the entity being modeled,assuming that the entity has a natural identifier.
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51
An entity cluster is considered "virtual" or "____________________" in the sense that it is not actually an entity in the final ERD.
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52
____________________ completeness means that not every supertype occurrence is a member of a subtype.
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53
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 trap
D) fan trap
A) surrogate primary keys
B) time-variant data
C) design trap
D) fan trap
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54
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-attribute
D) security compliant
A) unique values
B) nonintelligent
C) preferably single-attribute
D) security compliant
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55
The _________________________ is the result of adding more semantic constructs to the original entity relationship (ER)model.
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56
Disjoint subtypes are also known as ____________________ subtypes.
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57
____ relationships occur when there are multiple relationship paths between related entities.
A) Redundant
B) Duplicated
C) Time-variant
D) Supertype
A) Redundant
B) Duplicated
C) Time-variant
D) Supertype
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58
____________________ completeness means that every supertype occurrence must be a member of at least one subtype.
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59
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
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
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60
Subtypes that contain nonunique subsets of the supertype entity set are known as ____________________ .
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61
The main concern with redundant relationships is that they remain ____________________ across the model.
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62
In what two cases are composite primary keys particularly useful?
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63
The most common design trap is known as a(n)____________________.
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64
Explain the "no change over time" characteristic of a good primary key.
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65
Describe specialization and generalization.
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66
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.
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67
From a data modeling point of view,____________________ refer to data whose values change over time and for which you must keep a history of the data changes.
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68
What is an entity cluster?
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69
What do specialization hierarchies do?
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70
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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