Consider the relation scheme R = {E, F, G, H, I, J, K, L, M, N} and the set of…
2025
Consider the relation scheme R = {E, F, G, H, I, J, K, L, M, N} and the set of functional dependencies {{E, F} -> {G}, {F} -> {I, J}, {E, H} -> {K, L}, K -> {M}, L -> {N} on R.
What is the key for R ?
- A.
{E, F}
- B.
{E, F, H}
- C.
{E}
- D.
{E, F, H, K, L}
Attempted by 128 students.
Show answer & explanation
Correct answer: B
To find the key, compute the closure of attribute combinations. Start with {E,F,H} since E and F appear on left sides but H does not.
EFH+ = EFH + G (from EF->G) + IJ (from F->IJ) + KL (from EH->K) + M (from K->M) + N (from L->N), giving all attributes.
No proper subset of {E,F,H} determines all attributes, so the key is {E,F,H}.