Since I am going to TA an intro to databases class soon I might very well use it. Why not try to integrate it into a wikibook so that other people can contribute and extend it?
I'm happy that you consider it good enough, I hope it serves you well. About making it a wikibook, I've not explored that option at all till now but I am open to contribution. That is why I chose the OPL for it. I made it into a PDF since I knew Troff and that seemed like the easiest format to get it out there.
I've been looking for something to get me started on SQL. I'll give this a read and provide a more detailed comment as I finish it.
Then thank you in advance for the after finish comment :) I hope the book is beneficial to you.