Parallel Resonance circuit Q factor formula Clarification
I'm confused with the formula of Q factor in parallel resonance
  because in other books its different


In the first case, they are talking about the Q factor of a perfect inductor, L in parallel with a resistor. In the second case they are talking about the Q factor of a resistor in series with the inductor, L.

I know it can be confusing and some websites don't make this explicitly clear.