Microservice architecture: single database owned by a single service?

We're rebuilding a system in a microservice archiecture. I know the standard practice for SOA is to have each individual service responsible for its own database.

However, does it make sense to have one 'database' service responsible for handling a monolithic database (i.e. holding users, orders, inventory, etc in one db)? Is this something that's considered reasonable?

Or is the expectation that users, orders, inventory will all have their own separate databases and according services? If that's the case, how do I handle it when I want to do a simple relational query like ordering a list of inventory by how many orders we've had for each item?