functional dependency

Question

Let the relation R(X, Y, Z, A, B) with given functional dependencies
X -> YZ
Z -> A
A -> B
AZ -> X
The number of super keys possible__________ ?

Please answer with an explanation.

Comments

I got 24 Super Key

Answer 1

plz look into this one!!!

Answer 2

24 bcz candidate key are X,Z so 2^4+2^4-2^3  {X2^(n-1)+Z2^(n-1)-2^(n-2)}

OR

Direct (Superkey Among Prime)*2^(n-2) #Of non prime key

3*2^(5-2)

24

Comments

Can you tell me how did you get this? I am not aware of such formula. Direct me to your source.

Answer 3

THE BEST METHOD FOR CALCULATING NO OF SK's:

total no of sk's= (# sk's over prime attributes) *  (2^#no of non-prime)

here ck's are { X , Z }

# SK's over prime attributes are= { X , Z , XZ } =3 SK's over prime attributes

non-prime attributes are Y , A , B =3

total no of sk's= 3*(2^3)

=24 SK's