EXAM3 Solution

# EXAM3 Solution - Database Management Systems(CIS...

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1 Database Management Systems (CIS 4301) (Spring 2008) Instructor: Dr. Markus Schneider TA: Ganesh Viswanathan Wenjie Yuan Exam 3 Solutions Name: UFID: Email Address: Pledge (Must be signed according to UF Honor Code) On my honor, I have neither given nor received unauthorized aid in doing this assignment. _______________________________________________Signature For scoring use only: Maximum Received Exercise 1 8 Exercise 2 12 Exercise 3 10 Exercise 4 40 Exercise 5 30 Total 100

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2 Exercise 1 (Knowledge Questions) [8 points] 1. Give the definition of Boyce-Codd Normal Form (BCNF). [2 points] Solution: A relation schema R with FDs F is in Boyce-Codd normal form (BCNF), if, and only if, it is in 3NF and for each FD A B F at least one of the following conditions holds: B A, i.e., the FD A B is trivial. A is superkey of R. 2. What is the purpose of normal forms? [2 points] Answer: They are the basis of the normalization process which analyzes a given relation schema and based on their functional dependencies and primary keys, achieves the desirable properties of minimizing redundancy and minimizing insertion, deletion and update anomalies. 3. When is a 3NF relation not in BCNF? [2 points] Answer: Candidate keys in the relation are composite keys (they are not single attributes) There is more than one candidate key in the relation, and The keys are not disjoint, that is, some attributes in the keys are common. 4. Argue that, if R is in 3NF and every key is simple, then R is in BCNF. [4 points] Answer: Since every key is simple, we know that for any FD that satisfies X A, where A is part of some key, implies that A is a key. By the definition of a FD, if X is known, then A is known. This means that if X is known, we know a key for the relation, so X must be a superkey. This satisfies all of the properties of BCNF.
3 Exercise 2 (Multiple Choice) [12 points] (1).A given relation is known to be in third normal form, if: C A. All attributes contribute to the primary key. B. Each non-key attribute determines the primary key. C. Each non-key attribute is determined by the primary key. D. Every determinant is a candidate key. E. The relation is not in BCNF. (2) To transform a relation from first normal form to second normal form we must remove which one of the following. A. All partial-key and transitive dependencies. E B. All inverse partial-key dependencies. C. All repeating groups. D. All transitive dependencies. E. None of the above. (3) If the relation W(a,b,c,d,e) with the FD c a was normalized to BCNF, the best resulting relations of that process are … D A. W (c, b , d, e ) W1 (c , a) B. W (a, b , c, d, e) W1 (c , a) C. W (a, b , d, e) W1 (c, a) D. W (b , c, d, e) W1 (c , a) E. None of the above. (4).

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EXAM3 Solution - Database Management Systems(CIS...

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