ST_PointN

ST_PointN takes a linestring or a multipoint and an index as input parameters and returns that point in the linestring or multipoint that is identified by the index. The resulting point is represented in the spatial reference system of the given linestring or multipoint.

If the given linestring or multipoint is null or is empty, then null is returned.

Syntax

Parameters

geometry: A value of type ST_LineString or ST_MultiPoint that represents the geometry from which the point that is identified by index is returned.
index: A value of type INTEGER that identifies the nth point that is to be returned from geometry. If the index is smaller than 1 or larger than the number of points in the linestring or multipoint, then null is returned and a warning is returned (SQLSTATE 01HS2).

Return type

db2gse.ST_Point

Example

The following example shows the use of ST_PointN:


SET CURRENT FUNCTION PATH = CURRENT FUNCTION PATH, db2gse
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) )

SELECT id, CAST ( ST_AsText (ST_PointN (line, 2) ) AS VARCHAR(60) ) SECOND_INDEX
  FROM sample_lines

Results:


ID        SECOND_INDEX
--------- --------------------------------
        1 POINT (5.00000000 5.00000000)