ST_LineMerge-PolarDB(PolarDB)-阿里云帮助中心

Merges the line elements of a MultiLineString into one or more LineString objects by joining them at shared endpoints.

Syntax

geometry ST_LineMerge(geometry amultilinestring);

Parameter	Description
`amultilinestring`	The geometry object to merge.

ST_LineMerge accepts MultiLineString and LineString objects.

Note

Passing any geometry type other than MultiLineString or LineString returns an empty GeometryCollection.

Warning

ST_LineMerge drops the m coordinates of the input geometry.

Merging two connected line segments

The two input segments share the endpoint (2 1), so ST_LineMerge joins them into a single LineString.

SELECT ST_AsText(ST_LineMerge(ST_GeomFromText('MULTILINESTRING((1 1,2 1),(2 1,2 2))')));

Output:

        st_astext
-------------------------
 LINESTRING(1 1,2 1,2 2)
(1 row)