Question

I have a relation

R = (S, T, U, V, W, X, Y, Z) which has the FD’s

TW -> Y
TW -> Z
Y -> X
Y -> S
V -> U
X -> T

I’m trying to find the candidate key for R but because of the relationship

TW -> Y -> X -> T

I can’t figure out what it is. I know it has to have ‘V’ and ‘W’ in it but I don’t know if I should also have ‘X’ or ‘T’.

Answer 1

You say that W is dead sure inside any candidate key.

Therefore,

TW -> Y -> X -> T

becomes

T -> Y -> X -> T

So, which one do you choose, X or T?

And why not Y ?