Functional Dependency and Attribute Closure - Geeksfor Geeks PDF

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Functional Dependency and Attribute Closur Functional Depen A functional dependency A->B in a relation holds if two tuples having same va ple, in relation STUDENT shown in table 1, Functional Dependencies

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How to 2nd Candidate Keys and Super K If attribute closure of an attribute set contains all attributes of relation, th If no subset of this attribute set can functionally determine all attributes using FD set of table 1, (STUD_NO, STUD_NAME)+ = {STUD_NO, STUD_NAME, STUD_PHONE, STUD_S (STUD_NO)+ = {STUD_NO, STUD_NAME, STUD_PHONE, STUD_STATE, STUD_C (STUD_NO, STUD_NAME) will be super key but not candidate key because its STUD_NO will be a candidate key. GATE Question: Consider the relation scheme R = {E, F, G, H, I, J, K, L, M, M} {E, H} -> {K, L}, K -> {M}, L -> {N} on R. What is the key for R? (GATE-CS-2014 A. {E, F} B. {E, F, H} C. {E, F, H, K, L} D. {E} Answer: Finding attribute closure of all given options, we get: {E,F}+ = {EFGIJ} {E,F,H}+ = {EFHGIJKLMN} {E,F,H,K,L}+ = {{EFHGIJKLMN} {E}+ = {E} {EFH}+ and {EFHKL}+ results in set of all attributes, but EFH is minimal. So it w How to check whether an FD can be de To check whether an FD A->B can be derived from an FD set F, 1. Find (A)+ using FD set F. 2. If B is subset of (A)+, then A->B is true else not true. GATE Question: In a schema with attributes A, B, C, D and E following set of {A -> B, A -> C, CD -> E, B -> D, E -> A} Which of the following functional dependencies is NOT implied by the above

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