ST_MakeLine
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Name

ST_MakeLine — Creates a LineString from Point, MultiPoint, or LineString geometries.

Synopsis

geometry ST_MakeLine(geometry geom1, geometry geom2);

geometry ST_MakeLine(geometry[] geoms_array);

geometry ST_MakeLine(geometry set geoms);

Description

Creates a LineString containing the points of Point, MultiPoint, or LineString geometries. Other geometry types cause an error.

Variant 1: accepts two input geometries

Variant 2: accepts an array of geometries

Variant 3: aggregate function accepting a rowset of geometries. To ensure the order of the input geometries use ORDER BY in the function call, or a subquery with an ORDER BY clause.

Repeated nodes at the beginning of input LineStrings are collapsed to a single point. Repeated points in Point and MultiPoint inputs are not collapsed. Components of MultiLineString are handled in the order they appear in the collection. ST_RemoveRepeatedPoints can be used to collapse repeated points from the output LineString.

This function supports 3d and will not drop the z-index.

Availability: 3.7.0 - Support for MultiLineString input elements was introduced

Availability: 2.3.0 - Support for MultiPoint input elements was introduced

Availability: 2.0.0 - Support for LineString input elements was introduced

Availability: 1.4.0 - ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle more points faster.

Examples

Two-input variant.

Create a line composed of two points.

Code
SELECT ST_MakeLine(ST_Point(1, 2), ST_Point(3, 4));
Output
LINESTRING(1 2,3 4)
Figure
Geometry figure for visual-st-makeline-01

Create a 3D line from two 3D points.

Code
SELECT ST_MakeLine(ST_MakePoint(1, 2, 3), ST_MakePoint(3, 4, 5));
Output
LINESTRING(1 2 3,3 4 5)
Figure
Geometry figure for visual-st-makeline-02

Create a line from two disjoint LineStrings.

Code
SELECT ST_MakeLine('LINESTRING(0 0,1 1)', 'LINESTRING(2 2,3 3)');
Output
LINESTRING(0 0,1 1,2 2,3 3)
Figure
Geometry figure for visual-st-makeline-03

Array variant.

Create a line from an array formed by a subquery with ordering.

Code
SELECT ST_MakeLine(ARRAY(SELECT ST_Centroid(geom) FROM visit_locations ORDER BY visit_time));

Create a 3D line from an array of 3D points

Code
SELECT ST_MakeLine(ARRAY[ST_MakePoint(1, 2, 3), ST_MakePoint(3, 4, 5), ST_MakePoint(6, 6, 6)]);
Output
LINESTRING(1 2 3,3 4 5,6 6 6)
Figure
Geometry figure for visual-st-makeline-04

Aggregate variant.

This example queries time-based sequences of GPS points from a set of tracks and creates one record for each track. The result geometries are LineStrings composed of the GPS track points in the order of travel.

Using aggregate ORDER BY provides a correctly-ordered LineString.

Code
SELECT gps.track_id, ST_MakeLine(gps.geom ORDER BY gps_time) AS geom
FROM gps_points AS gps
GROUP BY gps.track_id;

When ordering within the aggregate is not possible, ordering in a subquery can be used. However, sometimes the query plan may not respect the order of the subquery.

Code
SELECT gps.track_id, ST_MakeLine(gps.geom) AS geom
FROM (
  SELECT track_id, gps_time, geom
  FROM gps_points
  ORDER BY track_id, gps_time
) AS gps
GROUP BY gps.track_id;