Name
ST_NumInteriorRings — Return the number of interior rings of a polygon geometry.
Synopsis
integer ST_NumInteriorRings(geometry a_polygon);
説明
Return the number of interior rings of a polygon geometry. Return NULL if the geometry is not a polygon.
This method implements the SQL/MM specification. SQL-MM 3: 8.2.5
Changed: 2.0.0 - in prior versions it would allow passing a MULTIPOLYGON, returning the number of interior rings of first POLYGON.
例
-- 通常のポリゴンの場合
SELECT gid, field1, field2, ST_NumInteriorRings(the_geom) AS numholes
FROM sometable;
-- マルチポリゴンの内環の総数を知りたい場合
SELECT gid, field1, field2, SUM(ST_NumInteriorRings(the_geom)) AS numholes
FROM (SELECT gid, field1, field2, (ST_Dump(the_geom)).geom As the_geom
FROM sometable) As foo
GROUP BY gid, field1,field2;