The illustration below shows examples of Polygon instances.

As shown in the illustration:

1. Figure 1 is a Polygon instance whose boundary is defined by an exterior ring.
   
2. Figure 2 is a Polygon instance whose boundary is defined by an exterior ring and two interior rings. The area inside the interior rings is part of the exterior of the Polygon instance.
   
3. Figure 3 is a valid Polygon instance because its interior rings intersect at a single tangent point.
   

The following example creates a simple geometry Polygon instance with a hole and SRID 10.

DECLARE @g geometry;
SET @g = geometry::STPolyFromText('POLYGON((0 0, 0 3, 3 3, 3 0, 0 0), (1 1, 1 2, 2 1, 1 1))', 10);

An instance that is not valid may be entered and converted to a valid geometry instance. In the following example of a Polygon, the interior and exterior rings overlap and the instance is not valid.

DECLARE @g geometry;
SET @g = geometry::Parse('POLYGON((1 0, 0 1, 1 2, 2 1, 1 0), (2 0, 1 1, 2 2, 3 1, 2 0))');

In the following example, the invalid instance is made valid with MakeValid().

SET @g = @g.MakeValid();
SELECT @g.ToString();

The geometry instance returned from the above example is a MultiPolygon.

MULTIPOLYGON (((2 0, 3 1, 2 2, 1.5 1.5, 2 1, 1.5 0.5, 2 0)), ((1 0, 1.5 0.5, 1 1, 1.5 1.5, 1 2, 0 1, 1 0)))

Concepts

Other Resources

Help and Information