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CS403 Database Management Systems GDB Solution Fall 2013

Suppose there are two entities “building” and “apartment”. The entity “apartment” is dependent entity and cannot exist independently and “building” is an independent entity. The “apartment” entity contains the primary key (building_name) of building entity to identify the apartment of that specific building. The “apartment” entity also has its own identifier, i.e. apartment_no but that identifier is not sufficient to identify the particular apartment, so in this case we used both keys building_name and apartment_no to identify the particular apartment.

You have studied different dependencies in the course.You are required to choose the appropriate dependency applicable in  the above scenario. Justify your answer with reasons.

Solution: 

Identifier Dependency is applicable here. It means that the dependent entity incase of existence dependency does not have its own identifier and any external identifier is used to pick data for that entity. And to define a key in this entity the key of the parent entity is to be used in the key for this entity may be used as composite keys.The entity “apartment” is dependent entity and cannot exist independently and “building” is an independent entity.

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