(21) Discuss the difference between existence dependency and identification dependency?

Question: Discuss the difference between existence dependency and identification dependency?   [signinlocker] SOLUTION Total participation of an entity type in a relationship type is defined as existence dependency. Identification dependency is existence dependency where a weak entity type is always dependent on the unique identifier...
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(19) Why can total participation of an entity type in a relationship type also be referred to as existence dependency of that entity type in that relationship type?

QUESTION: Why can total participation of an entity type in a relationship type also be referred to as existence dependency of that entity type in that relationship type?   [signinlocker] SOLUTION Total participation occurs if, in order to exist, an entity type must participate in...
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(14) What is the value of using role names to describe the participation of an entity type in a relationship type?

QUESTION: What is the value of using role names to describe the participation of an entity type in a relationship type?   [signinlocker] SOLUTION Role names can be used to clarify the nature of the participation of each entity type involved in a relationship type....
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(12) What is a relationship type? How does a relationship type differ from a relationship instance?

QUESTION: What is a relationship type? How does a relationship type differ from a relationship instance?   [signinlocker] SOLUTION A relationship type is a meaningful association among entity types. A relationship instance is an occurrence of a relationship type. [/signinlocker]
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(11) Give an example of three entity types and accompanying attributes that might be associated with a database for a car rental agency?

QUESTION: Give an example of three entity types and accompanying attributes that might be associated with a database for a car rental agency?   [signinlocker] SOLUTION VEHICLE (VehicleID, LicensePlate#, Make, Model, Year, Mileage, …) RENTER (License#, Name, Address, City, State, Zipcode, Insurance, etc.) VEHICLE_RENTAL (VehicleID,...
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(8) What is the difference between a key attribute and a non-key attribute?

QUESTION: What is the difference between a key attribute and a non-key attribute?   [signinlocker] SOLUTION A key attribute is an attribute that is part of a unique identifier. A non-key attribute is one that is not a constituent part of any unique identifier. [/signinlocker]
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(7) What is a unique identifier of an entity type? Is it possible for there to be more than one unique identifier for an entity type?

QUESTION: What is a unique identifier of an entity type? Is it possible for there to be more than one unique identifier for an entity type?   [signinlocker] SOLUTION An attribute, atomic (i.e., simple) or composite, whose values are distinct for each entity in the...
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