* attention. This article refers to something very much under development and known to be buggy *
If you have an existing model in the form of SQL CREATE statements you may find this file useful:
http://mdp.cti.depaul.edu/AlterEgo/default/download/document.file.075074495458.py/auto.py
Given a file myfile.sql that contains some table definitions in SQL, run
python auto.py myfile.sql
and it will make web2py models and Create Read Update Delete (CRUD) controllers for all your tables.
You will have to manually cut and paste the output in you app, edit the models to fix reference fields(incorrectly rendered as integer) and add validators.