(24) Define the term partial key?

Question: Define the term partial key?   [signinlocker] SOLUTION A partial key is an identifier of a weak entity type. By itself, it is not a “unique” identifier, but when combined with the unique identifier of the identifying parent of the weak entity type, it uniquely identifies weak entities. [/signinlocker]

(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 of its identifying parent for its unique identification. [/signinlocker]

(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 the relationship. Thus, total participation of an entity type in…

(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, License#, Dateout, Datein, Mileageout, Mileagein) [/signinlocker]