STWithin (geography Data Type)
SQL Server 2012
Returns 1 if a geography instance is spatially within another geography instance; otherwise, returns 0.
The following example uses STWithin() to test two geography instances to see if the first instance is completely within the second instance.
DECLARE @g geography;
DECLARE @h geography;
SET @g = geography::Parse('POLYGON ((-120.533 46.566, -118.283 46.1, -122.3 47.45, -120.533 46.566))');
SET @h = geography::Parse('CURVEPOLYGON (COMPOUNDCURVE (CIRCULARSTRING (-122.200928 47.454094, -122.810669 47.00648, -122.942505 46.687131, -121.14624 45.786679, -119.119263 46.183634), (-119.119263 46.183634, -119.273071 47.107523), CIRCULARSTRING (-119.273071 47.107523, -120.640869 47.569114, -122.200928 47.454094)))');
SELECT @g.STWithin(@h);