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(A: Geometry, B: Integer)

Since: v1.2.1

Examples:

SELECT ST_PointN(df.geometry, 2)
FROM df

Input: LINESTRING(0 0, 1 2, 2 4, 3 6), 2

Output: POINT (1 2)

Input: LINESTRING(0 0, 1 2, 2 4, 3 6), -2

Output: POINT (2 4)

Input: CIRCULARSTRING(1 1, 1 2, 2 4, 3 6, 1 2, 1 1), -1

Output: POINT (1 1)