The Moodle 2.2 Database Schema "reverse engineered" from the installed database using
MySQL Workbench http://www.mysql.com/products/workbench. For more about Moodle see http://www.moodle.org
For more about the Moodle database structure see
http://docs.moodle.org/dev/Database_schema_introduction
Marcus Green 2015

A Mysql MWB File that can be modified. moodle22.mwb A pdf rendering moodle22_erd.pdf.

How the diagram was created, Diagram FAQ.

Moodle 2.2 ER Diagram