candidate key

Question

Q1)  R(A1,A2,A3,..................An)  having A1A2 as its candidate key. Find the no of super key..?

Q2)   R(A1,A2,A3,..................An)  having A1 and A2 as its candidate key. Find the no of super key..?

Answer 1

The no of super keys are :

1. A₁A₂ is a candidate key so the there are n-2 in (A₁A₂A3................An) ,therefore the super key is 2^(n-2).

2.In this 2nd problem both A₁ and A₂ are seperate, so that 2(2^(n-1))-2^(n-2​).