ST_POINTN

Returns a Point at a specified index in a LineString.

SQL Syntax

ST_POINTN(<geometry>, <index>)

Arguments

ArgumentsDescription
<geometry>The argument must be an expression of type GEOMETRY that represents a LineString.
<index>The index of the Point to return.

:::note The index is 1-based, and a negative index is uesed as the offset from the end of LineString. If index is out of bounds, the function returns an error. :::

Return Type

Geometry.

SQL Examples

SELECT
  ST_POINTN(
    ST_GEOMETRYFROMWKT(
      'LINESTRING(1 1, 2 2, 3 3, 4 4)'
    ),
    1
  ) AS pipeline_pointn;

┌─────────────────┐
│ pipeline_pointn │
├─────────────────┤
│ POINT(1 1)      │
└─────────────────┘

SELECT
  ST_POINTN(
    ST_GEOMETRYFROMWKT(
      'LINESTRING(1 1, 2 2, 3 3, 4 4)'
    ),
    -2
  ) AS pipeline_pointn;

┌─────────────────┐
│ pipeline_pointn │
├─────────────────┤
│ POINT(3 3)      │
└─────────────────┘