31. Which of the following is used to express database consistency? a. Primary keys b. Functional dependencies c. Check clause d. All of the mentioned
 Answer: (d).All of the mentioned

 32. Which of the following is not a condition for the third normal form in the case of X→Y? a. X→ Y is trivial b. X is the superkey for R c. Each attribute in Y-X is a candidate key for R d. Each attribute in X-Y is a candidate key for R
 Answer: (d).Each attribute in X-Y is a candidate key for R

 33. F+ is called as the ________ of F a. Closure b. Sum c. Cartesian product d. None of the mentioned
 Answer: (a).Closure

 34. State true or false: A functional dependency must first satisfy the second normal form to satisfy the third normal form. a. True b. False c. May be d. Can't say
 Answer: (a).True

 35. State true or false: The fourth normal form does not exist and it is instead called as the BCNF. a. True b. False c. May be d. Can't say
 Answer: (b).False

 36. A functional dependency f on R is _______ by a set of functional dependencies F on r if every instance of r(R) that satisfies f also satisfies F. a. Logically Defined b. Logically Derived c. Logically implied d. None of the mentioned
 Answer: (c).Logically implied

 37. If F is a set of functional dependencies, then the closure of F is denoted by? a. F* b. Fo c. F+ d. F
 Answer: (c).F+

 38. If a functional dependency is reflexive, B is a subset of A and A is the set of attributes, then a. B→A holds b. A→B holds c. AB→C holds d. None of the mentioned
 Answer: (b).A→B holds

 39. State true or false: Armstrong’s axioms allow us to generate all F+ for any given F a. True b. False c. May be d. Can't say
 Answer: (a).True

 40. Armstrong axioms are called sound because? a. They are expensive b. They cannot generate correct functional dependencies c. They allow us to generate the complete closure d. They cannot generate incorrect functional dependencies
 Answer: (d).They cannot generate incorrect functional dependencies

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