H2GIS

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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