Hi Scott, I hope it can help, it should extract the sql and pk/fk relationships for whatever modules you have the code for.  I have just slightly updated the code in github so there is a little more information in the readme file and it adds a comment into the SQL indicating what the version of Moodle was that generated it. The output file is hard coded to be called component.sql and it gets put into the same folder as the source, i.e. moodle\components\sqlgenerator.  Neither are awesome design choices but I was using the JFDI methodology. Let me know if it works for you or if you have any problems.

There is a python script in there somewhere that helps generate the layout of the diagram, but that could do with a little more work (my first ever python code).

By the way the diagram *.mwb file over at examulator contains about 18 more detailed expanded diagrams of some of the sub-modules of Moodle (i.e. diagrams for badges, courses events etc.) I might get myself a big poster of the diagram from zazzle or similar.

If anyone is desperate for a diagram for Moodle 2.7 put your requests here.

I have updated my ER (Entity Relationship) diagram visible at 

http://www.examulator.com/er

It is based on "reverse engineering" the code from a fresh install of Moodle 3.0. It includes relationships not included in the source code and documented here

https://tracker.moodle.org/browse/MDL-49795

Where I have created more detailed diagrams of subsections I have included clickable links via a drill down icon. 

It is available as png and pdf but if you are a developer I strongly recommend you install MySQL workbench and open the mwb file provided.

Share and Enjoy (Cyrius Cybernetics 1978™ )