that query has already been answered by --current-db switch in sqlmap or select db_name() query.
How to Hack a server through its DB a.k.a pwnage
well , first of all edit your question and hide the website address as we do not promote unauthorized hacking (its baaad)
as you shared a windows server , although you did not share the connected user but I assume its a SYSTEM account which means that it has admin rights on the server , so there is nothing hard now , is it ?
just use --os-shell switch in sqlmap to get your self a command console , from there you can add a new user with admin rights , check if RDP is open .. if not open that or even spawn a PowerShell (refer to my powershell archive hacks and techniques )
–os-shell: SQLMap will try to get the operating system command shell by exploiting SQL injection
with the above you can wreak havoc