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Consider the following relation: R (A1, A,2, ....., An) and Every (n – 2) attributes of R forms Candidate key. Which of the following represents the number of super keys are there in R ?
a.   nCn–2 * 22 b.   nCn–2 + n + 1 c. nCn–2 * [3] d. nCn–2

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Best answer
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given that Every (n – 2) attributes of R forms Candidate key. 
so no. of super key =
every (n – 2)  combination out of n OR every (n – 1)  combination out of n OR every (n )  combination out of n
=ncn-2 + ncn-1 +ncn
=  ncn-2 +n+1
B is correct

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