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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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