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    PolarDB:ST_LineSubstring

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    PolarDB:ST_LineSubstring

    Last Updated:Mar 28, 2026

    Returns the part of a line between two fractional locations.

    Syntax

    geometry  ST_LineSubstring(geometry  aLinestring, float8 startfraction, float8 endfraction);
geography ST_LineSubstring(geography aLinestring, float8 startfraction, float8 endfraction);

    Parameters

    ParameterDescription
    aLinestringThe LineString to extract a substring from.
    startfractionThe start position.
    endfractionThe end position.

    Usage notes

    • If startfraction and endfraction are equal, the function behaves identically to ST_LineInterpolatePoint.

    • To extract a substring from a MultiLineString, first use ST_LineMerge to merge its LineStrings into a single LineString.

    • 3D objects are supported. z coordinates are preserved.

    • m coordinates are supported.

    Examples

    Geometry

    Extract the middle third of a line using the geometry type.

    SELECT ST_AsText(ST_LineSubstring('LINESTRING(0 0,10 10)'::geometry, 0.3, 0.6));

    Result:

          st_astext
---------------------
 LINESTRING(3 3,6 6)
(1 row)

    Geography

    SELECT ST_AsText(ST_LineSubstring('LINESTRING(0 0,10 10)'::geography, 0.3, 0.6));

    Result:

                                   st_astext
--------------------------------------------------------------------------------
 LINESTRING(2.97227762767668 3.01417970957332,5.96094221033023 6.0199989936211)

    See also