ST_Z

ST_Z returns the z coordinate of an input point.

Syntax

ST_Z(point)

Arguments

point

A POINT value of data type GEOMETRY.

Return type

DOUBLE PRECISION value of the m coordinate.

If point is null, then null is returned.

If point is a 2D or 3DM point, then null is returned.

If point is the empty point, then null is returned.

If point is not a POINT, then an error is returned.

Examples

The following SQL returns the z coordinate of a point in a 3DZ geometry.

SELECT ST_Z(ST_GeomFromEWKT('POINT Z (1 2 3)'));

st_z
-----------
 3                

The following SQL returns the z coordinate of a point in a 4D geometry.

SELECT ST_Z(ST_GeomFromEWKT('POINT ZM (1 2 3 4)'));

st_z
-----------
 3