Tutorial 4: ER Diagram

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Tutorial 4 ER Diagram
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• Question.
• Complete the diagram to capture the following
  constraints
• Each student must take exactly one course.
• Every course must be taken by at least one
  student.

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• Complete the diagram to capture the following
  constraints
• Each student must take exactly one course.
• Every course must be taken by at least one
  student.

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• Question. Which design is better and why?

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redundancy in office_number and office-location
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• Question. What are the differences in the
  following two designs?

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• In the first diagram, accounts can be created
  without customers/branches. This is not possible
  in the second design.
• In the first diagram, many customers can share
  the same account. This is also not possible in
  the second one.

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• Question. What are the primary keys for the three
  relationships, respectively?

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• owns license
• participated license
• involved driver-id, report-number

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• Question. Complete the following diagram to
  satisfy these constraints
• Every director must have directed some movie, but
  not every actor has played in a movie.
• Each director/actor may have directed/played in
  multiple movies.
• Each movie is directed by a single director.
• Not every movie has a sequel.

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