STSymDifference (geometry Data Type)
Returns an object representing all points that are either in one geometry instance or another geometry instance, but not those points that lie in both instances.
Is another geometry instance in addition to the instance on which STSymDistance() is being invoked.
SQL Server return type: geometry
CLR return type: SqlGeometry
This method always returns null if the spatial reference IDs (SRIDs) of the geometry instances do not match.
The following example uses STSymDifference() to compute the symmetric difference of two Polygon instances.
DECLARE @g geometry; DECLARE @h geometry; SET @g = geometry::STGeomFromText('POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))', 0); SET @h = geometry::STGeomFromText('POLYGON((1 1, 3 1, 3 3, 1 3, 1 1))', 0); SELECT @g.STSymDifference(@h).ToString();