I'm just finishing something of a large migration from an old Xoops site to Drupal. I've not had to get too down and dirty with the Xoops database, for which I'm quite happy as it wasn't so coherent after lots of upgrades and customisations. I've made a small migration handbook for myself which could be handy for folks.

Migrating the data in on it's own would have been pretty simple from just following the basic node import note. What was done here was much more, and interesting because of it.

The sites data was spread all over the database tables, and often not recorded in it's own field but just within the content itself. So the migration was built up with lots of scripts to pull out and enter into CCK fields all the links, youtube videos, pictures and files.

All of a sudden a wealth of resources that people have added to the site and lost in a mountain of data suddenly become easily to search, filter and display in different forms. Well worth the extra time it took to run all the content through.