I have seen all the 9 tables related to a forum in this diagram. A screenshot of the relevant part of the diagram is as follows.
The question is that how can I find out what columns are there in each of these tables? I tried to google it, but could not find a list of columns in the tables.
Download and install MySql Workbench
https://dev.mysql.com/downloads/workbench/
Then download the latest database schema from here
https://docs.moodle.org/dev/Database_Schema