Are more than one correct Lewis structures possible (not counting resonance)?

I am currently learning chemical bonding, specifically Lewis structures. And these nitrogen oxides, nitrogen-oxygen ions and other atoms showing variable oxidation states are confusing me. As many examples I have understood with bonding atoms having no $d$ or $f$ orbitals, the variable oxidation states are a result of dative bonds. 


So when drawing the Lewis structure for $\ce{NO3-}$, I drew:


![Nitrate ion - my structure](https://i.stack.imgur.com/A5rIG.png)


My book however has only one dative bond, and has this structure:


![Nitrate ion - book's structure](https://i.stack.imgur.com/cBnnG.png)


To me, both of them look correct. The octets seem to be satisfied in both cases.


So my questions are:


1. Are both of them correct? If yes, how?
2. If my structure is incorrect, what rule am I violating?




As $\ce{O}$ is more electronegative than $\ce{N}$ the $\ce{1-}$ charge in the $\ce{O-N}$ will be on the oxygen. Even if it were to be a dative bond, its donation in an electron pair makes it very easy for oxygen to take. Oxygen is, after all, an oxidising agent.


 2