Database management

Question

Que- R(ABCD) and fds are { A->B ,B->C,C->A} then number of candidate key is........?

Explain please

Comments

IT will be 3 {AD, CD, BD}

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Can you please explain??

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D is the Multi value Attribute, so it will be in every CK, and From the FD's we can easily see that A, B and C defining each other.

So, CK {AD, BD, CD}.

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Thanks bro

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y u said d ismultivalued? if any attribute not present in fd that means that attribute is multivalued??

please exlain.

Answer 1

Closure of A ,B and C give = ABC but D is missing so Candidate key will be AD ,BD,CD now we take closure of AD = ABCD , BD = ABCD , CD = ABCDso we get all attributes of Relation so AD is candidate key