- The first and last points in a polygon will be the same point.
- A polygon consists of one exterior ring and zero or more interior rings. The interior rings must lie completely within the exterior ring. A MultiPolygon is a group of non-overlapping polygons.
- The element ID of each point identifies which element the point belongs to in a Multi-type geometry. For example, for a MultiLineString that contains two LineStrings, the first LineString will be element 1 and the second LineString will be element 2.
For non-Multi geometries, the element ID is always 1.
- If an input geometry value is NULL, the corresponding output row that is returned will have NULLs in the geomType, x, y, and z columns.
- Due to the hierarchical nature of the ID columns, you can use an ORDER BY clause to keep the rows associated with each passed-in geometry together, and grouped according to the sub-geometries of Multi types. See the example below.