Well eventually someone was gonna ask this. Can you connect to MS-SQL using Mapserver? Of course thanks to GDAL/OGR anything is possible. OGR’s Virtual Spatial Data can be used to connect to SQL Server database. http://www.gdal.org/ogr/drv_vrt.html

One can connect via OGR ODBC driver directly by creating a view with an additional WKT column from your x, y fields and add this view to the GEOMETRY_COLUMNS table in your database http://www.gdal.org/ogr/drv_odbc.html