CPSC 304 2004 MIDTERM 2 SOLUTIONS

# CPSC 304 2004 MIDTERM 2 SOLUTIONS - CPSC304Midterm2...

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CPSC 304 Midterm 2 Nov 10, 2004 Total: 17 points Question 1 (9 points) The donations relation was defined based on the following SQL statement: CREATE TABLE donations (recipientName CHAR(20) NOT NULL, donorOrganization CHAR(20) NOT NULL, organizationType CHAR(20), amount REAL, PRIMARY KEY (recipientName, donorOrganization) ) For each of the following relational calculus queries, determine if there exists an equivalent relational algebra statement. If you answer is positive, give such a statement; otherwise, just state that no such statement exists. (You may get part marks if you write down in English the correct meaning of each query.) a) { < N > | x, y (<N, x, tobacco, z > donations and <N, y, tobacco, r> donations and x y) } (2 points) Recipients who received donations from at least 2 distinct tobacco organizations. π A.recipientName A.recipientName =B.recipientName ° A.organizationType = tobacco ° B.organizationType = tobacco ° A.donorOrganization <> B.donorOrganization [ ρ A (donations) · ρ B (donations)] b) { < N > | x ( <r , x, tobacco, s > donations <N , x, tobacco, t > donations) }

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