Is it possible to have just one DB across all services - Lemmy.zip

I’m pretty new to the self hosting thing but I’m enjoying it a lot and want to go a bit further down the proverbial rabbit hole. I’m looking at a bunch of services and they all require a DB, usually a MySQL DB. It seems counterintutitive to have 20 MySQL databases each in its own Docker container. So is there a way to have one DB across most of my services? (I realize that Nextcloud and other bigger items should have a dedicted DB.) How would I set up a shared DB in a docker-compose file?