ST_CurvePolygon If the geometry-expression is of type ST_CurvePolygon, return the geometry-expression. If the geometry-expression is a geometry collection with a single element of type ST_CurvePolygon, return that element. If the geometry-expression is the empty set, return an empty set of type ST_CurvePolygon. Otherwise, raise an exception condition.
Examples
Example 1 –
The following example returns the result Polygon ((0 0, 2 0, 1 2, 0 0)).