ST_Z

Definition

ST_Z takes an ST_Point as an input parameter and returns its z- (elevation) coordinate. In SQLite, ST_Z can also update the z-coordinate of an ST_Point.

Syntax

Oracle and PostgreSQL

sde.st_z (geometry1 sde.st_point)

SQLite

st_z (geometry  geometryblob)
st_z (input_shape geometryblob, new_Zvalue double)

Return type

Oracle

Number

PostgreSQL

Integer

SQLite

Double precision is returned when ST_Z is used to return the z-coordinate of a point. A geometryblob is returned when ST_Z is used to update the z-coordinate of a point.

Example

The z_test table is created with two columns: the id column, which uniquely identifies the row, and the geometry point column. The INSERT statement inserts a row into the z_test table.

The SELECT statement lists the id column and the double-precision z-coordinate of the point inserted with the previous statement.

Oracle

CREATE TABLE z_test (
 id integer unique,
 geometry sde.st_point
);

INSERT INTO z_test (id, geometry) VALUES (
 1,
 sde.st_point (2, 3, 32, 5, 4326)
);

SELECT id, sde.st_z (geometry) Z_COORD
 FROM Z_TEST; 

        ID      Z_COORD

         1        32

PostgreSQL

CREATE TABLE z_test (
 id integer unique,
 geometry sde.st_point
);

INSERT INTO z_test (id, geometry) VALUES (
 1,
 sde.st_point (2, 3, 32, 5, 4326)
);

SELECT id, sde.st_z (geometry) 
 AS Z_COORD
 FROM z_test; 

        id      z_coord

         1        32

SQLite

CREATE TABLE z_test (id integer);

SELECT AddGeometryColumn(
 NULL,
 'z_test',
 'pt1',
 4326,
 'pointzm',
 'xyzm',
 'null'
);

INSERT INTO z_test (id, pt1) VALUES (
 1,
 st_point (2, 3, 32, 5, 4326)
);

SELECT id, st_z (pt1) 
 AS "The z coordinate"
 FROM z_test; 

id      The z coordinate

1        32.0

The ST_Z function can also be used to update the coordinate value of an existing point. In this example, ST_Z is used to update the z-coordinate value of the first point in z_test.

UPDATE z_test
 SET pt1=st_z(
  (SELECT pt1 FROM z_test where id=1), 32.04)
 WHERE id=1;