I would start by reading many of the old posts/articles/stairways on this site.

I have been a DBD/artichect for ~ 15 years and I still manage to learn some new trick/syntax/way of thinking from one or more of the posters on this site at least weekly.

I also try and go to a few of the blogs/sites from some of the top posters (or at least the posters that I learn the most from) a few times per month to see if they posted anything interesting.

It sounds like you are a developer. If so, it would do you worlds of good to read up about what DBA's do.

IMHO, having a good understanding of what your teammates (DBA's, artichect's, developers) do will help you write more efficient code for your system.

Finally, pick an area of SQL that you don't have much knowledge in and work to understand and master it.