In SQL Server 2012 a polygon is consists of an exterior ring with zero or some interior rings. So every simple polygon (rectangle, square and ...) must have an exterior ring and
From MSDN:
The following criteria are needed for a ring to be acceptable.
- The LineString instance must be accepted.
- The LineString instance must have at least four points.
- The starting and ending points of the LineString instance must be the same.
So what if I want to declare a triangle with three points in SQL Server 2012?