Unformatted text preview: given relation R of size N? Mark a single answer on the answer sheet (not here!). [3pt]
a. 2 N
b. 4 N
c. N2
d. 2N2
e. 2N c The size of a cross product is the product of the two relations, so it’s just N2. 9. True or False: A ⋈θ B = σθ (A × B). Mark the answer sheet (not here!). [1pt] True. This is the precise definition of theta join given in the lecture slides. If it were a natural join, you’d have to add a projection too. 10. True or False: (A ∪ B) ∪ (C — D) = (B ∪ (A ∪ (C — D))). Mark the answer sheet (not here!). [1pt] True. Unions are commutative and associative. 11. True or False: (A ∩ (B — C)) ∩ D) = (A ∩ ((C — B) ∩D)). Mark the answer sheet (not here!). [1pt] False. Subtraction is not commutative. 5 III. Sorting [11 points]
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 Fall '08
 Staff
 Relational model, Pages, Join, Composition of relations

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