ST_InteriorRingN

Definition

St_InteriorRingN returns the nth interior ring of a polygon as an ST_LineString.

The order of the rings cannot be predefined since the rings are organized according to the rules defined by the internal geometry verification routines and not by geometric orientation. If the index exceeds the number of interior rings possessed by a polygon, a null value is returned.

Syntax

Oracle

sde.st_interiorringn (pl1 sde.st_polygon, INDEX integer)

Return type

ST_LineString

Example

Create a table, sample_polys, and add a record.

CREATE TABLE sample_polys (id integer, geometry sde.st_geometry);

INSERT INTO sample_polys VALUES (
1,
sde.st_polygon ('polygon ((40 120, 90 120, 90 150, 40 150, 40 120), (50 130, 60 130, 60 140, 50 140, 50 130), 
(70 130, 80 130, 80 140, 70 140, 70 130))', 0)
);

Select the ID and the geometry of the interior ring.

Oracle

SELECT id, sde.st_astext (sde.st_interiorringn (geometry, 2)) Interior_Ring
FROM SAMPLE_POLYS; 

ID INTERIOR_RING 

1  LINESTRING (70.00000000 130.00000000, 70.00000000 140.00000000, 80.00000000 140.00000000, 80.00000000 130.00000000, 70.00000000 130.00000000)

PostgreSQL

SELECT id, sde.st_astext (st_interiorringn (geometry, 2)) 
AS Interior_Ring
FROM sample_polys; 

id interior_ring

1  LINESTRING (70 130, 70 140, 80 140, 80 130, 70 130)