I’ll be making one for my gamemode eventually if there isn’t one already. If you need one sooner then the answer is: you would need to implement certain functionality for it to be loadable as a module.
I was thinking PostgreSQL because that’s what I know. I can’t really wrap my head around NoSQL implementations. The one thing I can’t stand is MySQL, and that’s about all I can see available for networking data in Garrysmod.
Subquery handling is my primary problem. After a certain point, it starts becoming useless with subqueries. This isn’t so much a problem with Garry’s Mod, since most implementations are basic, but it still irks me. Another is the lack of standards support. MySQL is not at all even close to resembling standards, which means if you build specific to MySQL, you can never leave MySQL. As well, and this applies less to Garry’s Mod, there’s less reliability, and in general, I find it harder to get support for specific problems.