ST_X function

The ST_X function takes a point as an input parameter and returns its X coordinate. You can optionally indicate an X coordinate as input parameter in addition to the point and the function returns the point itself with its X coordinate set to the specified value.

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

Syntax

Parameters

point: A value of type ST_Point for which the X coordinate is returned or modified.
x_coordinate: A value of type DOUBLE that represents the new X coordinate for point.

Return types

DOUBLE, if x_coordinate is not specified
ST_Point, if x_coordinate is specified

Examples

Example 1

This example illustrates use of the ST_X function. Geometries are created and inserted into the SAMPLE_POINTS table.


CREATE TABLE sample_points (id INTEGER, geometry ST_Point)

INSERT INTO sample_points (id, geometry)
  VALUES (1, ST_Point (2, 3, 32, 5, 1) ),
         (2, ST_Point (4, 5, 20, 4, 1) ),
         (3, ST_Point (3, 8, 23, 7, 1) )

Example 2

This example finds the X coordinates of the points in the table.


SELECT id, ST_X (geometry) X_COORD
  FROM sample_points

Results:


ID         X_COORD
---------- ------------------------
         1   +2.00000000000000E+000
         2   +4.00000000000000E+000
         3   +3.00000000000000E+000

Example 3

This example returns a point with its X coordinate set to 40.


SELECT id, CAST( ST_AsText( ST_X (geometry, 40)) AS VARCHAR(60) )
  X_40
  FROM sample_points
  WHERE id=3

Results:


ID     X_40
------ ----------------------------------------------------------
     3 POINT ZM(40.000000 8.000000 23 7)