ST_ToPoint function

The ST_ToPoint function takes a geometry as an input parameter and converts it to a point. The resulting point is represented in the spatial reference system of the specified geometry.

The specified geometry must be empty or a point. If the specified geometry is null, then null is returned.

Syntax

Parameter

geometry: A value of type ST_Geometry or one of its subtypes that represents the geometry that is converted to a point.
A geometry can be converted to a point if it is empty or a point. If the conversion cannot be performed, then an exception condition is raised (SQLSTATE 38SUD).

Return type

ST_Point

Example

This example creates three geometries in SAMPLE_GEOMETRIES and converts each to a point.


CREATE TABLE sample_geometries (id INTEGER, geometry ST_Geometry)

INSERT INTO sample_geometries
  VALUES (1, ST_Geometry ('point (30 40)', 1) ),
         (2, ST_Geometry ('linestring empty', 1) ),
         (3, ST_Geometry ('multipolygon empty', 1) )

In the following SELECT statement, the ST_ToPoint function is used to return points converted to ST_Point from the static type of ST_Geometry.


SELECT CAST( ST_AsText( ST_ToPoint(geometry) ) AS VARCHAR(35) ) POINTS
  FROM sample_geometries

Results:


POINTS
---------------------------------
POINT (30.000000 40.000000)
POINT EMPTY
POINT EMPTY