Database systems 1. (20 POINTS) Please answer the following questions. 1.A) (5 P

Question

Database systems

1. (20 POINTS) Please answer the following questions. 1.A) (5 POINTS) What does an entity type represent in an ER model? Give one example for each entity type that has either physical or conceptual existence 1.B.) (10 POINTS) What does a relationship type represent in an ER model? Give examples of unary, binary, and ternary relationships. 1.C.) (5 POINTS) A relationship type that involves four entities is called a quaternary relationship. Can you think of an example of a quaternary relationship?

Explanation / Answer

An Entity is something that has real world existence(either Physical or Conceptual). For example a Book , Users of a website or a car. An entity has attributes which are properties of an entity. For example , Title is an attribute for Book entity.

Relationship is the means by which two(or more) entities are connected.

eg. Student(entity) enrolled in (relationship) Course(entity) one to one relationship

      Book(entity) written by(relationship) Author(entity) many to one relationship

Employee(entity) works on(relationship) Project(entity) many to many relationship

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