How to use external database as backend

How to use external database as backend

We have all Accounts and Contacts data on a MSSQL (Microsoft SQL Server) that is continuosly updated by our Account Managers. I understan I can inport such data via CSV but we rather prefer to have a SCP-MSSQL live connection (read only would be sufficient).
 
How it is possible to do that? I did not find it in the Documentation.
 
Thanks


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