Nome
ST_InteriorRingN — Returns the Nth interior ring (hole) of a Polygon.
Sinossi
geometry ST_InteriorRingN(geometry a_polygon, integer n);
Descrizione
Restituisce una LINESTRING che rappresenta l'anello esterno per una geometria POLYGON. Restituisce NULL se la geometria non è un poligono. Non funziona con MULTIPOLYGON
![[Nota]](../images/note.png)
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Non funzionerà per i MULTIPOLYGON. Da utilizzare assieme a ST_GeometryN o ST_Dump per i MULTIPOLYGON |
Questo metodo implementa le OGC Simple Features Implementation Specification for SQL 1.1.
Questo metodo implementa la specifica SQL/MM. SQL-MM 3: 8.2.6, 8.3.5
Questa funzione supporta il 3d e non distrugge gli z-index.
Esempi
Code
WITH data AS (
SELECT ST_BuildArea(ST_Collect(
ST_Buffer(ST_Point(1, 2), 20, 3),
ST_Buffer(ST_Point(1, 2), 10, 3)
)) AS geom
)
SELECT geom AS input_polygon,
ST_InteriorRingN(geom, 1) AS ring
FROM data;
Output
POLYGON((21 2,18.320508075688775 -7.999999999999998,11.000000000000002 -15.320508075688771,1 -18,-8.999999999999996 -15.320508075688775,-16.32050807568877 -8.000000000000007,-19 2,-16.320508075688778 11.999999999999995,-9.000000000000009 19.320508075688767,1 22,10.999999999999986 19.32050807568878,18.320508075688767 12.000000000000009,21 2),(11 2,9.660254037844384 7.000000000000004,5.999999999999993 10.66025403784439,1 12,-4.000000000000004 10.660254037844384,-7.660254037844389 6.999999999999997,-9 2,-7.660254037844386 -3.000000000000004,-3.999999999999998 -6.660254037844387,1 -8,6.000000000000001 -6.660254037844386,9.660254037844387 -2.999999999999999,11 2)) | LINESTRING(11 2,9.660254037844384 7.000000000000004,5.999999999999993 10.66025403784439,1 12,-4.000000000000004 10.660254037844384,-7.660254037844389 6.999999999999997,-9 2,-7.660254037844386 -3.000000000000004,-3.999999999999998 -6.660254037844387,1 -8,6.000000000000001 -6.660254037844386,9.660254037844387 -2.999999999999999,11 2)
Figure