CMPS182_Summer2017_MidtermWithAnswers.pdf

CMPS182_Summer2017_MidtermWithAnswers.pdf - Midterm Exam...

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Midterm Exam CMPS 182, Summer 2017, UCSC August 3, 2017 STUDENT ’S NAME: _________________________________________________________________________ STUDENT ’S CRUZID (first part of email): ______________________________________________ Part Score Max Part Score Max 1 30 4 28 2 10 5 18 3 14 Part I (30 points): Query Results Questions 1-6 are about the Bars domain tables, which are being provided on 2 separate sheets of paper. What is the result of each of the following queries? (Show attribute names at the top in all results. If the query does not specify ORDER BY then any order will do.) Question 1 (4 points): SELECT Name, Capacity FROM Bars WHERE Zip = 95010; Answer 1 : Name Capacity ------------------------------------------------ Relational Expressions 8 SUM of the Parts 10 Question 2 (4 points): SELECT DISTINCT City, Zip FROM Bars WHERE Capacity >= 20; Answer 2 :
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City Zip ----------------------------------- Santa Cruz 95064 Monterey 93940 San Francisco 94101 San Francisco 94102 Question 3 (5 points): SELECT Beer FROM Bars, Sells WHERE Bar = Name AND City = ‘Santa Cruz’ INTERSECT SELECT Beer FROM Bars, Sells WHERE Bar = Name AND City = ‘ Woodside ; Answer 3 : Beer ------------ Heineken Sapporo Question 4 (5 points): SELECT Beer, MAX(Price) FROM Sells GROUP BY Beer; Answer 4 : Beer MAX(Price) ------------------------------------------ Budweiser 4.00 Molson Golden 6.00 Heineken 7.00 Sapporo 6.00 Question 5 (6 points): SELECT DISTINCT S1.Bar FROM Sells S1 WHERE S1.Price < ALL (SELECT S2.Price FROM Sells S2 WHERE S2.Bar = ‘Select Clientele’ ) ;
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Answer 5 : S1.Bar --------- Chugs and Slugs Hi Bar Question 6 (6 points) (a query expressed in relational algebra): Drinker, Beer ( Frequents.Bar = Sells.Bar AND Sells.Price > 6.50 (Frequents x Sells)) Answer 6 : Drinker Beer --------------------------------- Barack Heineken Dmitri Heineken PART II (10 points). YES/NO and multiple-choice, 1 point each. Circle the correct answer for each question (or circle the letter next to the answer, whichever you prefer). Question 7: If we assume that {Bar, Beer} is the primary key for the attached Sells table, what can we say about {Bar, Beer, Price}? a. It could be declared as UNIQUE b. It is a key c. It is a super key d. None of the above Answer 7: b. It is a super key Question 8 : The purpose of indexing is to maintain consistency between tables. a. YES b. NO Answer 8: NO Question 9 : Which of the following is most likely to be a reasonable primary key for the Bars table?
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a. {Name} b. {City} c. {City, Zip} d. {City, Zip, Capacity} Answer 9: a. {Name} Question 10 : There can be multiple keys for a relation.
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