Tutorial 4: Functional Dependency

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Tutorial 4 Functional Dependency
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• Question. Let R be a relation with schema A, B,
  C, D, E, on which the following functional
  dependencies hold
• A ? BC, CD ? E, B ? D, E ? A.
• Compute the closure of CD.
• Also do we have B ? E?

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• Question. Let R be a relation with schema A, B,
  C, D, E, on which the following functional
  dependencies hold
• A ? BC, CD ? E, B ? D, E ? A.
• List all the candidate keys of R.

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• Question. Consider relation R(title, theater,
  city) where
• title is the name of a movie,
• theater is the name of a theater playing the
  movie, and
• city is the city where the theater is located.
• We know
• Different cities cannot have theaters with the
  same name.
• Different theaters in the same city cannot play
  the same movie.
• Write the functional dependencies implied by the
  above assumptions.
• If we decompose R into (title, theater) and
  (theater, city), is this a legal decomposition?

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• Question. Consider table TABLE(A, B, C). Write an
  SQL query to test whether A ? B holds.
• Given two answers, one containing a nested query
  and the other not.