ST_Force3DM - PolarDB - Alibaba Cloud Documentation Center

This topic describes the ST_Force3DM function. This function forcefully converts a geometry object into a 3D object.

Syntax

geometry  ST_Force3DM(geometry  geomA);


Parameter	Description
geomA	The geometry object that you want to specify.

If the input geometry object does not contain m coordinates, the values of m coordinates of the output geometry object are specified as 0.
If the input geometry object contains z coordinates, z coordinates are removed from the output geometry object.
This function supports circular strings and curves.

Obtain a 3D object by using the default parameter settings.

SELECT ST_AsEWKT(ST_Force3DM(ST_GeomFromEWKT('POINT(1 2)')));
   st_asewkt
---------------
 POINTM(1 2 0)
(1 row)

Execute the following statement to obtain a 3D object for which the z coordinates are removed from the input geometry object:

SELECT ST_AsEWKT(ST_Force3DM(ST_GeomFromEWKT('POINT(1 2 3)')));
   st_asewkt
---------------
 POINTM(1 2 0)
(1 row)