As of UBB.threads 7.7.2 a simple 1-click utility is built-in to accomplish the database transactions for you.
Control Panel > Content Rebuilder > Update Forum URL References from HTTP to HTTPS
This updates all existing Main Forum URL references from HTTP to HTTPS (SSL). This action includes posts, private topics, profile comments, signatures, and user avatars.
It is all described in the "Transition Your Forum From HTTP to HTTPS" post here:https://www.ubbcentral.com/forums/u...transition-your-forum-from-http-to-https