Database Test 3 Computer Subject
Database Test 3 Computer Subject
Question 31
An identifier of an entity instance?
An identifier must be unique or may be unique to identify an entity instance correctly.
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Question 32
Which type of identifier is used to identify a set of instances of a given entity?
A non-unique identifier is used to identify multiple instances of the same entity type.
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Question 33
Depending on the system being modeled, a relationship can have entities?
A relationship can involve one, two, or more entities depending on the degree of the relationship.
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Question 34
The degree of a relationship refers to the:
The degree of a relationship specifies how many entities participate in it.
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Question 35
A weak entity is one which _____?
A weak entity depends on a strong entity for its existence and cannot exist independently.
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Question 36
A subtype entity_____?
A subtype inherits attributes from the supertype and may contain additional optional attributes.
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Question 37
Cardinality expresses number of entity occurrences associated with one occurrence of the related entity
Cardinality specifies the exact number of entity occurrences that can be associated with another entity occurrence.
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Question 38
Knowing _____ the number of entity occurrences is very helpful at application software level.
Knowing the maximum and minimum cardinalities helps in application logic and database design.
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Question 39
A _____ attribute need not be physically stored within the database
Derived attributes are calculated from other stored attributes and do not need to be physically stored.
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Question 40
A _____ relationship exists when 3 entities are associated.
A ternary relationship involves three entities simultaneously in a relationship.
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