Hi Adam,
i would strongly advice you to *not* work directly on the SharePoint database!
Lots of reasons not to:
There is no guarantee that the data model wont change tomorrow (thats why MS supplied an API)
Updating could also corrupt your database (for example if you update some but not all referenced foreign keys)
Not covered by Support if issues emerge
Also there is no need:
Theres plenty of other ways to do this, including WebDAV, FP-RPC (frontpage remote procedure calls) and SPS Web Services / Custom Web services.
Please explain in more details what you are trying to do. If you want to view and edit data from a custom list in SharePoint, use the UpdateListItems method of the SPS Lists web service (try opening
http://<your portal>/<your area>/_vti_bin/lists.asmx in your browser to get a list of methods)
I recently posted some data about this to another user in this forum, so search for UpdateListItems and you should find some sample code on how to achieve this through managed code.
I advice you to download the SPPT SDK for reference.
http://www.microsoft.com/downloads/details.aspx?FamilyId=AA3E7FE5-DAEE-4D10-980F-789B827967B0&displaylang=en
hth
AndersR