ST_NumInteriorRings

Signatures

INT ST_NumInteriorRings(GEOMETRY geom);

Description

Return the number of interior rings of the first POLYGON in the geometry. This will work with both POLYGON and MULTIPOLYGON. Return NULL if there is no polygon in the geometry.

Examples

SELECT ST_NumInteriorRings('POLYGON((0 0, 10 0, 10 6, 0 6, 0 0),
                                    (1 1, 2 1, 2 5, 1 5, 1 1),
                                    (8 5, 8 4, 9 4, 9 5, 8 5))');
-- Answer: 2

SELECT ST_NumInteriorRings('MULTIPOLYGON(
                                ((0 0, 10 0, 10 6, 0 6, 0 0),
                                ((1 1, 2 1, 2 5, 1 5, 1 1)),
                                ((8 5, 8 4, 9 4, 9 5, 8 5)))');
-- Answer: 0

SELECT ST_NumInteriorRings('MULTIPOLYGON(
                                ((0 0, 10 0, 10 6, 0 6, 0 0),
                                 (1 1, 2 1, 2 5, 1 5, 1 1)),
                                ((1 1, 2 1, 2 5, 1 5, 1 1)),
                                ((8 5, 8 4, 9 4, 9 5, 8 5)))');
-- Answer: 1

SELECT ST_NumInteriorRings(
     'GEOMETRYCOLLECTION(
        MULTIPOINT((4 4), (1 1), (1 0), (0 3)),
        LINESTRING(2 6, 6 2),
        POLYGON((1 2, 4 2, 4 6, 1 6, 1 2)))');
-- Answer: 0

SELECT ST_NumInteriorRings(
     'GEOMETRYCOLLECTION(
        MULTIPOINT((4 4), (1 1), (1 0), (0 3)),
        LINESTRING(2 6, 6 2),
        POLYGON((1 2, 4 2, 4 6, 1 6, 1 2),
                (2 4, 3 4, 3 5, 2 5, 2 4)))');
-- Answer: 1

See also