As I understand Eric shows how to connect to a standalone Salesforce database server.
Is there a way to create a linked server to "Salesforce as a Service" database at https://login.salesforce.com ?
I think your understanding isn't correct - as far as I am aware, there is no 'stand alone' salesforce DB, it's always delivered 'as a service' The linked server approach works for prod (salesforce.com) and also sandboxes (test.salesforce.com).