Or ONLY Sql and be "The best SQL guy?"
Is it better go be a mile wide and 1 inch deep, or a mile deep and 1 inch wide?
It depends on the kind of job you're looking for. For an early stage startup the "width" is relatively more important (but obviously the deeper the better too). Meanwhile for a bigger company with a lot more fellow coders the "depth" is relatively more important (but the more width the better too obviously).
I think you should go deep, but not with a certain technology. Think about it a bit differently and go deep in an area.
Remember, technologies change fast, there will always be new platforms, new DB types (just think about Big Data and their adoption rate in the latest years). You will not be safe if you master a technology, but if you master a domain you will have deep knowledge on the subject and you will be quick(er) to adapt to any new technology coming your way.
Best of luck!