Connecting to SQL Server Spatial

First we need to create a server:

CREATE SERVER fdw_sqlserver_test 
  FOREIGN DATA WRAPPER ogr_fdw 
  OPTIONS ( 
    datasource 'MSSQL:server=CM_DOM\MSSQLSERVER12;database=hgis;UID=postgres_fdw;PWD=postgres_fdw', 
    format 'MSSQLSpatial'); 

If you're using Postgre SQL 9.5+, you can use the IMPORT SCHEMA command:

IMPORT FOREIGN SCHEMA "dbo.Wig100_skorowidz" 
FROM SERVER fdw_sqlserver_test INTO data_linked; 

Otherwise you will have to specify the table schema explicitly:

CREATE FOREIGN TABLE data_linked.dbo_wig100_skorowidz 
   (fid integer , 
    geom public.geometry , 
    oid integer , 
    gid integer , 
    version integer , 
    godlo character varying , 
    nazwa character varying , 
    nazwa2 character varying , 
    kalibracja character varying , 
    pas real , 
    slup real ) 
   SERVER fdw_sqlserver_test 
   OPTIONS (layer 'dbo.Wig100_skorowidz'); 

At this stage, you should be able to query the foreign table as if it was local.