test1.pdf - 1 instructoru2019s solution DATABASE SYSTEMS...

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1instructor’s solution:DATABASE SYSTEMSCSCI 331, section 37, class # 11749CSCI 711, section 37, class # 11750Test # 1July 25, 2019instructor: Bojana Obreni´cNOTE:It is the policy of the Computer Science Department to issue a failing grade in thecourse to any student who either gives or receives help on any test.To pass this test, you are required to follow in full the test protocol described below:Queens College photo-IDis required;this is aclosed-booktest, to which it isforbiddento bring any material except pencils (pens) and erasers—in particular, bringing any electronic device is a direct violation of the test protocol;student namehas to be writtenclearlyoneach pageof the problem set during thefirst five minutes ofthe test—there is a penalty ofat least 1 pointfor each missing name;answersshould be written only in the space marked “Answer:” that follows the statement of the problem(unless stated otherwise);yourhandwritingmust be legible so as to leave no ambiguity whatsoever as to what exactly you have written;any problem to which you givetwo or more (different) answersreceives thegrade of zeroautomatically;if you have written something into the answer space bymistake,cross it out completely or erase itandit will not be graded;scratchshould never be written in the answer space, but may be written on the (empty) back of the problempages, the content of whichwill not be graded;when requested,hand inthe problem set;once you leavethe classroom, you cannot come back to the test;You may work on as many (or as few) problems as you wish. Good luck.time: 70 minutes.full credit:70 points (corresponds to normalized score of 100%.)C: 28 points (corresponds to normalized score of 40%.)problem:01020304050607normalized scoregrade [points]:%
2Problem 1[ 32 points ]Consider the relationalschemaR=ABCDEHJwith the set of functionaldependenciesF(which is a minimal cover) given asfollows.(1)AHJ
(4)CHB(5)CJASchemaRis decomposed intoR1andR2such that:R1=ACDHJandR2=BCDEH(Reminder:Answers missing the required proof arenot creditable.)(a)Findallcandidate keys ofR, and prove that eachone indeed is a candidate key and that there are noothers.Hint:Apply the algorithm straightforwardlyto confirmtwocandidate keys; then observe a fastway to prove there are no others.

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