Name
ST_PointOnBoundary — Returns a Point guaranteed to lie on the geometry's boundary.
Synopsis
geometry ST_PointOnBoundary(bytea
Geometry);
Description
Returns a Point guaranteed to lie on the geometry's boundary. The boundary of a Point is the empty set, so this fuction will return null for Points.
![[Note]](images/note.png) | |
This method does not support GeometryCollection arguments |
Coordinate Dimensions
| 2D | 3D | M |
|---|---|---|
 | | |
Spatial Standards Support
| OGC SFS for SQL. 1.1 (1999) | OGC SFS for SQL. 1.1.0 (2005) | OGC SFS for SQL. 1.2.0 (2006) | SQL-MM Part 3 |
|---|---|---|---|
| - | - | - | - |
Examples
--MULTIPOINT
SELECT ST_PointOnBoundary(ga) from (SELECT ST_GeomFromText('MULTIPOINT (-10 30, 0 30, -10 20)') as ga) as foo;
--Result
null
--LINESTRING
SELECT ST_AsText(ST_PointOnBoundary(ga))
from (SELECT ST_GeomFromText('LINESTRING (0 0 20, 10 10 40, 10 5 60, 15 10 80)') as ga) as foo;
--Result:
POINT (0 0 20)
--POLYGON
SELECT ST_AsText(ST_PointOnBoundary(ga))
from (SELECT ST_GeomFromText('POLYGON ((10 30, 0 10, 30 20, 30 30, 20 40, 10 30))') as ga) as foo;
--Result:
POINT (30 20) |  |