ST_PointN

Introduction: Return the Nth point in a single linestring or circular linestring in the geometry. Negative values are counted backwards from the end of the LineString, so that -1 is the last point. Returns NULL if there is no linestring in the geometry.

Format: ST_PointN(geom: geometry, n: integer)

SQL example:

SELECT ST_PointN(ST_GeomFromText('LINESTRING(0 0, 1 2, 2 4, 3 6)'), 2) AS geom

Result:

+---------------------------------------------------------------+
|geom                                                           |
+---------------------------------------------------------------+
|POINT (1 2)                                                    |
+---------------------------------------------------------------+