To use ruby with mysql, you have to use the mysql module apparently.
So to make a simple graphical program that uses a database, you need ruby software, a book on ruby, mysql software, ruby mysql module, documents of the ruby mysql module, documents on ruby/tk.
Hmm. Thats a lot when you look at it really. It should go faster every time but theres a lot of work there for the first one. Not to mention that fact it wasnt clear straight off that a ruby book didnt cover ruby/tk or ruby mysql.