Descrizione

Returns the closure of the combinatorial boundary of this Geometry. The combinatorial boundary is defined as described in section 3.12.3.2 of the OGC SPEC. Because the result of this function is a closure, and hence topologically closed, the resulting boundary can be represented using representational geometry primitives as discussed in the OGC SPEC, section 3.12.2.

Eseguito dal modulo GEOS

	Prma della 2.0.0, questa funzione dava un'eccezione se usata con GEOMETRYCOLLECTION. A partire dalla 2.0.0 in poi, restituirà invece NULL (input non supportato).

Questo metodo implementa le OGC Simple Features Implementation Specification for SQL 1.1.

OGC SPEC s2.1.1.1

Questo metodo implementa la specifica SQL/MM.

SQL-MM IEC 13249-3: 5.1.17

Questa funzione supporta il 3d e non distrugge gli z-index.

Enhanced: 2.1.0 support for Triangle was introduced

Changed: 3.2.0 support for TIN, does not use geos, does not linearize curves

Esempi

Linestring with boundary points overlaid SELECT ST_Boundary(geom) FROM (SELECT 'LINESTRING(100 150,50 60, 70 80, 160 170)'::geometry As geom) As f; ST_AsText output MULTIPOINT((100 150),(160 170))

polygon holes with boundary multilinestring SELECT ST_Boundary(geom) FROM (SELECT 'POLYGON (( 10 130, 50 190, 110 190, 140 150, 150 80, 100 10, 20 40, 10 130 ), ( 70 40, 100 50, 120 80, 80 110, 50 90, 70 40 ))'::geometry As geom) As f; ST_AsText output MULTILINESTRING((10 130,50 190,110 190,140 150,150 80,100 10,20 40,10 130), (70 40,100 50,120 80,80 110,50 90,70 40))

SELECT ST_AsText(ST_Boundary(ST_GeomFromText('LINESTRING(1 1,0 0, -1 1)')));
st_astext
-----------
MULTIPOINT((1 1),(-1 1))

SELECT ST_AsText(ST_Boundary(ST_GeomFromText('POLYGON((1 1,0 0, -1 1, 1 1))')));
st_astext
----------
LINESTRING(1 1,0 0,-1 1,1 1)

--Using a 3d polygon
SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('POLYGON((1 1 1,0 0 1, -1 1 1, 1 1 1))')));

st_asewkt
-----------------------------------
LINESTRING(1 1 1,0 0 1,-1 1 1,1 1 1)

--Using a 3d multilinestring
SELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT('MULTILINESTRING((1 1 1,0 0 0.5, -1 1 1),(1 1 0.5,0 0 0.5, -1 1 0.5, 1 1 0.5) )')));

st_asewkt
----------
MULTIPOINT((-1 1 1),(1 1 0.75))

Si veda anche

ST_AsText, ST_ExteriorRing, ST_MakePolygon