Marcus Green January 2015
Generate sql statements from Moodle install to be used in generating ER diagrams. The morekeys.xml file is designed to contain any additional pk/fk relationships that do not appear in the code but you may consider are implied by the data. This uses the standard xml tags as defined by dbxml except it uses a convention whereby the first part of the name of the key contains the string erd to indicate that the first part is the table name. So for a key named user_preferences_erd_user_id the code would work out that this belonged in the user_preferences table.
Read more about this plugin here https://github.com/marcusgreen/moodle_local-sqlgenerator/wiki
The code only looks at the install files it does not interrogate the tables installs. I have done no checking for security issues at all so I recommend only running it on Moodle test installs. It loops through your source directories and so may have a significant performance impact (though probably only for a minute or so), so that's another reason for not running on a live system with real users.
You may need to increase the max_execution_time value in your php.ini. On a machine with 16GB of RAM and an i7 chip I put the value up to 360
The SQL code is called component.sql and output to the same folder as the code (i.e. moodle\local\sqlgenerator
To see diagrams generated from the output of this plugin see here
http://www.examulator.com/er/
To create the database that is used for the diagrams use this command line
mysql -umoodle -p -f < create_tables_moodle.sql
The -f parameter is to force the process to continue if errors occur. There is at least one error triggered by an anomoly in the primary/foreign keys