statistics - in the formula of the conditional probability, what would happen if the conditioning event be a null event? -

in formula of conditional probability,

p(a|b)=p(ab)/p(b)

what happen if conditioning event null event, i.e. p(b)=0 in formula?

thanks.

a non-existent event happens absolute certainty, probability 100%, thus

p(a|b) = p(a) / 1 = p(a) 

p(a|b) in case means there no condition @ all. side note, can see 3 same in situation:

p(a|b) = p(ab) = p(a)