Entity Relationship Diagram – the graphical representation of the Moodle database showing the connections between different tables and the relationship between each entity. Entity Relationship Diagram (ERD) Diagram gives you the visual representation of the data and how it is related to each other.
Marcus Green – Senior Analyst Developer at Moodle HQ, has updated the ERD diagram for Moodle 3.3 recently. Moodle ERD diagrams are a great help for Moodle developers to understand how Moodle stores data in tables and how those tables are related to each other.
The new updated version of the ERD Diagram is also created by reverse engineering from the source xml files using the MySQL Workbench tool. You can download the latest ERD diagram for Moodle 3.3 here.
The diagram was created by using the MySQL Workbench tool using a file containing the SQL code used to install Moodle. The SQL statements were extracted from the install.xml files from each Moodle module. To extract the SQL statements from XML, Marcus has written down a moodle utility plugin (Download here) which makes use of the Moodle XMLDB API.
Check out the ERD diagrams for earlier Moodle versions here.
Download the ERD Diagram in PDF format here.
Set of images of each component of the diagram including different components can be checked here.