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Unformatted text preview: CS411 Spring 2007 Midterm Solution Problem 1 (20 points) Multiple Choice For each of the following statements, choose ONE answer among A,B,C,D,E. You will get 2 points for each correct answer, 0 points for each incorrect answer. (1) Which one of the following is TRUE for E/R modeling? A. Supporting relations are used to define class hierarchies. B. Only entities can have attributes. C. Many-to-one relations cannot be precisely represented in E/R diagrams.- D. The key attributes of an entity can be on other entities. E. E/R models do not support class hierarchies of entities. Reference: cs411-LA-02-ER.pdf slide 46 (2) Which one of the following is TRUE for schema normalization? A. All relations in 3NF also satisfy BCNF.- B. 3NF decomposition is always dependency preserving. C. 4NF removes redundancies due to functional dependencies. D. For each Function Dependency, X Y , X is a key or super key is the definition for 3NF. E. Relations with only three attributes are automatically in BCNF. Reference: cs411-LA-05-RELDesignII.pdf slide 40 (3) Which one of the following is TRUE for Relational Algebra?- A. The projection operator may affect the number of tuples in set semantics. B. The rename operator may affect the number of tuples in bag semantics. C. Intersection is considered as one of the primitive operators. D. Join is considered as one of the primitive operators. E. Projection is only defined for bag semantics. Reference: cs411-LA-07-PHP-RelAlgebra.pdf slide 37 (4) In Relational Algebra, the join operator is equivalent to which one of the following? A. Selection operator followed by group operator. B. Disjoint operator followed by rename operator. C. Projection operator followed by selection operator. D. Intersection operator followed by Cartesian product operator.- E. Cartesian product operator followed by selection operator. Reference: cs411-LA-07-PHP-RelAlgebra.pdf slide 46 (5) Which one of the following is true for SQL? A. The UNION operator uses bag semantics by default. B. The SELECT-FROM-WHERE clauses use set semantics by default.- C. The ALL keyword is used to switch to bag semantics. D. Bag semantics is enabled with SET SEMANTICS=BAG....
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- Spring '07