This is an inaccurate statement. Not everything is written to a MySQL(MariaDB) database table. Some settings are only stored in the AstDB and some, like voicemail, aren’t even saved anywhere but the actual config file. Voicemail, for example, will just parse the voicemail file and then re-write it when things are saved.
That being said, there is no documentation to tell you that or to tell you what the actual DB structures, tables or schema’s are for those tables. There’s nothing that lays out things like Extensions use findmefollow, users and devices tables but only certain FollowMe or other settings are written to the SQL tables but some settings are only written to the AstDB database.
There also nothing that tells you the relationship of the SQL data to the AstDB data. For example, for FollowMe the “Use Call Confirmation” has the field of ‘needsconf’ in the SQL database that has a value of NULL or CHECKED (enabled) but in the AstDB which is checked via the dialplan the field is ‘grpconf’ and the values are empty (nothing set) or ENABLED. So you can’t count on an exact one to one relationship of what is in the SQL tables and what is written out into the dialplan/AstDB.
There is also nothing that covers what other modules impact user settings/details in the AstDB. Queues, Extension Routes, Parking Pro and I’m sure others all write information to a users AstDB profile that is called on via the dialplan or other actions.
I spent quite a bit of time just modifying settings in the GUI and then checking those changes against the dialplan, config files and AstDB to see exactly what was being done and the final results to figure out what is related to what.