Can't say that it is possible through sql manipulation coz it involves multiple users and multiple threads and forums and more like direct conversations and all that. Developers usually discourage such attempts as these are usually not something stored in single tables in database. Someone else might have a better idea about this.
Proper route is to use the link in the footer of each mail sent by the forum (
disable all emails.
is a link that is included in all alerts sent by the forum). Or on watched sections on the forum itself like these links here:
https://xenforo.com/community/watched/forums
https://xenforo.com/community/watched/threads
PS: This applies for already watched data. Changing watched setting for all members should be doable through a mysql command.
This might be useful:
https://xenforo.com/community/threa...ifications-for-every-user.219169/post-1666641
(I tried chatgpt but the mysql command it generated does not seem to show any results here so not posting the command it suggested)