If you have even the slightest interest in learning more about databases and how they are used, i say, dive right in my friend! start reading and trying to get your hands on various applications and get your hands dirty- play with it. This is pretty much how you go about anything you want to learn. IMO its the best way because you dont spend a ton of money on a class and half through you get discouraged and decide to try another career path. just my .02
SQL is great to learn, many many company's use this. Also PHP/MySQL is spreading like wild fire, maybe jump on the band wagon and see where it takes you.