ST_InteriorRingN

Determine the nth interior ring of a polygon geometry.

Syntax

ST_InteriorRingN(geo, n);

geo: The input geometry.
Type: ST_GEOMETRY(ANY)
n: The index, starting with 1, that identifies the interior ring.
Type: INT4

Returns

A value of type ST_GEOMETRY(ANY) that contains a line geometry, or NULL if there is no nth interior ring.

Examples

inza..ST_AsText(inza..ST_InteriorRingN(inza..ST_WKTToSQL('POLYGON ((0 0, 100 0, 100
            100, 0 100, 0 0), (10 10, 10 20, 20 20, 20 15, 10 10))'), 1));

ST_ASTEXT

---------
LINESTRING (10 10, 10 20, 20 20, 20 15, 10 10)
(1 row)

SELECT inza..ST_InteriorRingN(inza..ST_WKTToSQL('Polygon ((10 10, 10 20, 20 20, 20 15,
            10 10))'), 5);

ST_INTERIORRINGN
----------------
(1 row)