That something can be done it doesn’t mean you should do it. Sharing a database server over VPN using public Internet is ripe with problems.
SQL database servers are designed for fast and reliable local area networks where constant connection between client and server can be maintained. VPN tunnels often shut down when there is no traffic, which can break existing connections. Further, the performance leaves a lot to be desired due to encryption and other overheads. People complain – a Google search for “database over VPN problem” yields almost 8.5 million references.
When database content needs to be accessed by remote clients over the Internet, an HTTP(S) web service is most likely the best solution. HTTP was designed for wide area networks and automatically comes with benefits of efficient caching, easy content sharing and is accessible from virtually all programming environments.