This is OT, I'm considering buying the MySQL, Second Edition Paul DuBois
book. I'm using MySQL 3.23. Should I be buying the first edition DuBois
book instead or does BuBois cover both 3 and 4 in the second edition? Is
there a huge difference between 3 and 4?
Here's a URL for the second edition:
http://www.kitebird.com/mysql-book/
It discusses what's new in this edition. Paul DuBois is also very active on the MySQL mailing lists so your question would probably get a more detailed answer there. Also, in all likelihood, the first edition may not even be available anymore.
Larry