I find that rushing in is a big problem when learning SQL. I've actually seen people take a jump in and just start messing about trying to make databases without reading any documentation, in the small hope that they can "just pick it up as they go along".

Stop! Sit down, go to amazon and look up beginning sql. Choose a book on beginning sql, of which, might I recommend the Apress series, and when it arrives work through it. You won't be an expert at the end of it, but at least you'll know enough of the basics to have a starting knowledge.

And before anyone tells me that they don't have time to sit down and work through it, just think of how much time your going to waste when it all goes wrong. Get the basics right, and the rest will come to you a lot easier.