A lot of the interaction you do with the DB is done in Before Form pieces, Actionscripts and in the Integrator. It does need more documentation, you may find some of what you need by looking at the sample packages. Maybe do a search in the forum for ' JFactory::getDBO()' or ' $db->setQuery' or other code that talks to the DB.
Yesterday I added a new table to my Joomla database called 'jos_titleorders' and put the fields I needed into it. I will be using a Before Form piece to create a Joomla user, another script to log them in automatically, then the Integrator to add data to this new table.
You could do something similar by creating the tables you need, exporting the table to CSV in PHPMyAdmin, populating the data into the fields in Excel then re-importing the tabel into Excel. - There are probably easier ways to do that also, but I'm a SQL newbie.
Post a basic description of what you're trying to do and maybe some of us here on the forum can help.
Also, check out the Facebook Fan Page
Here. As it grows you'll find more and more solutions there.