| re: how to connect to a database by ruby, and modify, add or delete
Yes, you should be able to do that, but it will be MUCH easier to do if your database follows the rules for table names.
I'd suggest a look at some of the standard tutorials, or even (gasp) go get the 'official' ruby on rails book - go to http://www.rubyonrails.org/ and find the 'agile web development with rails' book. Shoot, you can even download it (for a price).
Since you ask only about ruby, and not rails, the 'other' main book on Ruby alone might be all you need. Again, google is your friend here - look for "Programming Ruby: the Pragmatic Programmer's Guide".
Note that, in my experience, the Rails book is enough to get you going, but not necessarily in the best direction. I'm still fighting with my web application, and I finally find out that I'm woefully messed up in handling the transition from 'thing on the web page that came from the database' to 'saving the changed thing back to the database' when the web page is of my creation and not of the scaffold....
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