ST_PointN - Amazon Redshift
SyntaxArgumentsReturn typeExamples
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ST_PointN

ST_PointN returns a point in a linestring as specified by an index value. Negative index values are counted backward from the end of the linestring, so that -1 is the last point.

The dimension of the returned geometry is the same as that of the input geometry.

Syntax

ST_PointN(geom, index)

Arguments

geom

A value of data type GEOMETRY or an expression that evaluates to a GEOMETRY type. The subtype must be LINESTRING.

index

A value of data type INTEGER that represents the index of a point in a linestring.

Return type

GEOMETRY of subtype POINT.

The spatial reference system identifier (SRID) value of the returned geometry is set to 0.

If geom or index is null, then null is returned.

If index is out of range, then null is returned.

If geom is empty, then null is returned.

If geom is not a LINESTRING, then null is returned.

Examples

The following SQL returns an extended well-known text (EWKT) representation of a six-point LINESTRING to a GEOMETRY object and returns the point at index 5 of the linestring. 

SELECT ST_AsEWKT(ST_PointN(ST_GeomFromText('LINESTRING(0 0,10 0,10 10,5 5,0 5,0 0)',4326), 5));

st_asewkt
-------------
 SRID=4326;POINT(0 5)