ST_StartPoint function

The ST_StartPoint function takes a curve as an input parameter and returns the point that is the first point of the curve.

The resulting point is represented in the spatial reference system of the specified curve. This result is equivalent to the function call ST_PointN(curve, 1)

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

Syntax

Parameters

curve: A value of type ST_Curve or one of its subtypes that represents the geometry from which the first point is returned.

Return type

ST_Point

Example

In the following example, two linestrings are added to the SAMPLE_LINES table. The first one is a linestring with X and Y coordinates. The second one is a linestring with X, Y, and Z coordinates. The ST_StartPoint function is used to return the first point in each linestring.


CREATE TABLE sample_lines (id INTEGER, line ST_LineString)

INSERT INTO sample_lines
  VALUES (1, ST_LineString ('linestring 
         (10 10, 5 5, 0 0, 10 0, 5 5, 0 10)', 0))

INSERT INTO sample_lines
  VALUES (1, ST_LineString ('linestring z 
         (0 0 4, 5 5 5, 10 10 6, 5 5 7, 0 0 8)', 0))

SELECT id, CAST( ST_AsText( ST_StartPoint( line ) ) AS VARCHAR(80))
  START_POINT
  FROM sample_lines

Results:


ID          START_POINT
----------- --------------------------------------------
          1 POINT (10 10)                                                         
          1 POINT Z(0 0 4)