ST_NumInteriorRing

Definition

ST_NumInteriorRings takes an ST_Polygon and returns the number of its interior rings.

Syntax

sde.st_numinteriorring (pl1 sde.st_geometry)

Return type

Integer

Example

An ornithologist wants to study a bird population on several south sea islands. She wants to identify which islands contain one or more lakes, because the bird species she is interested in feeds only in freshwater lakes.

The ID and name columns of the islands table identify each island, while the land ST_Polygon column stores the islands' geometry.

CREATE TABLE islands (id integer,
name varchar(32),
land sde.st_geometry);

INSERT INTO islands VALUES (
1,
'Bear',
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)
);

INSERT INTO islands VALUES (
2,
'Johnson',
sde.st_polygon ('polygon ((10 10, 50 10, 10 30, 10 10))', 0)
);

Because interior rings represent the lakes, the ST_NumInteriorRing function lists only those islands that have at least one interior ring.

Oracle

SELECT name
FROM ISLANDS
WHERE sde.st_numinteriorring (land)> 0;

NAME

Bear

PostgreSQL

SELECT name
FROM islands
WHERE sde.st_numinteriorring (land)> 0;

name

Bear