Name
ST_NumInteriorRings — Returnerar antalet inre ringar (hål) i en polygon.
Synopsis
integer ST_NumInteriorRings(geometry a_polygon);
Beskrivning
Returnerar antalet inre ringar i en polygongeometri. Returnerar NULL om geometrin inte är en polygon.
Denna metod implementerar SQL/MM-specifikationen. SQL-MM 3: 8.2.5
Ändrad: 2.0.0 - i tidigare versioner kunde man skicka en MULTIPOLYGON och få tillbaka antalet inre ringar i den första POLYGONEN.
Exempel
--If you have a regular polygon
SELECT gid, field1, field2, ST_NumInteriorRings(geom) AS numholes
FROM sometable;
--If you have multipolygons
--And you want to know the total number of interior rings in the MULTIPOLYGON
SELECT gid, field1, field2, SUM(ST_NumInteriorRings(geom)) AS numholes
FROM (SELECT gid, field1, field2, (ST_Dump(geom)).geom As geom
FROM sometable) As foo
GROUP BY gid, field1,field2;