ST_InteriorRingN — Returns the Nth interior ring (hole) of a Polygon.
geometry ST_InteriorRingN(
geometry a_polygon, integer n)
;
Returns the Nth interior ring (hole) of a POLYGON geometry as a LINESTRING. The index starts at 1. Returns NULL if the geometry is not a polygon or the index is out of range.
This function does not support MULTIPOLYGONs. For MULTIPOLYGONs use in conjunction with ST_GeometryN or ST_Dump |
This method implements the OGC Simple Features Implementation Specification for SQL 1.1.
This method implements the SQL/MM specification. SQL-MM 3: 8.2.6, 8.3.5
This function supports 3d and will not drop the z-index.
SELECT ST_AsText(ST_InteriorRingN(geom, 1)) As geom FROM (SELECT ST_BuildArea( ST_Collect(ST_Buffer(ST_Point(1,2), 20,3), ST_Buffer(ST_Point(1, 2), 10,3))) As geom ) as foo;