Sams Teach Yourself SQL in 10 Minutes - Ben Forta

Really nice for giving you the basics or filling in the gaps. Obviously it's not comprehensive and I would say don't let this be the extent of your learning, but it does give the basics for general SQL in a very easy to read format. I took a Database class in college in 2013 but I still found myself saying "Ohhhh, so THAT'S what that is. Why didn't my prof just say that?"