C=O bond length comparison among cyclohex‐2‐en‐1‐one and cyclohex‐3‐en‐1‐one I can see that in the first case a resonance would occur, and in the second case, there would be no resonance effect. I have read the fact that resonance reduces bond length due to partial double bond character. 

According to that, shouldn't the $\ce{C=O}$ bond length in 1 be lesser than that in 2? The answer in my book is that the $\ce{C=O}$ bond in 1 is longer (reason is simply given as: "Resonance"). Could someone help me understand what's going on here?
The case 1 has partial double bond character (due to resonance) while case 2 has total double bond character of the C-O bond. So, relative to case 2, the C-O bond length in case 1 is longer.