How to access company private and personal database over the

Question

The company wanted to use C# windows application for daily monitoring activities. I have developed the same. We have installed the sql server on their database server.

But users are all around the states and they wanted to install the application on their laptop or machine which is fine. But the thing is How can the application access the company private database server over the internet? It is against of company policy to expose the private and personal database over the internet. Firewall is also installed on their server.

Company wanted some other type of network for the application and database. Please help me out.