ST_ToMultiLine function

The ST_ToMultiLine function takes a geometry as an input parameter and converts it to a multilinestring. The resulting multilinestring is represented in the spatial reference system of the specified geometry.

The specified geometry must be empty, a multilinestring, or a linestring. If the specified geometry is null, then null is returned.

Syntax

Parameter

geometry: A value of type ST_Geometry or one of its subtypes that represents the geometry that is converted to a multilinestring.
A geometry can be converted to a multilinestring if it is empty, a linestring, or a multilinestring. If the conversion cannot be performed, then an exception condition is raised (SQLSTATE 38SUD).

Return type

ST_MultiLineString

Example

In the following example, the lines of results have been reformatted for readability. The spacing in your results will vary according to your online display

This example illustrates the use of the ST_ToMultiLine function.


CREATE TABLE sample_geometries (id INTEGER, geometry ST_Geometry)

INSERT INTO sample_geometries
  VALUES (1, ST_Geometry ('multilinestring ((0 10, 0 0, 10 0),
                                         (23 43, 27 34, 35 12))', 1) ),
         (2, ST_Geometry ('linestring z (0 10 1, 0 0 3, 10 0 5)', 1) ),
         (3, ST_Geometry ('point empty', 1) ),
         (4, ST_Geometry ('multipolygon empty', 1) )

In the following SELECT statement, the ST_ToMultiLine function is used to return multilinestrings converted to ST_MultiLineString from the static type of ST_Geometry.


SELECT CAST( ST_AsText( ST_ToMultiLine(geometry) )
  AS VARCHAR(130) ) LINES
  FROM sample_geometries

Results:


LINES
--------------------------------------------------------------
MULTILINESTRING (( 0.000000 10.000000, 0.000000 0.000000, 
                  10.000000 0.000000),(23.000000 43.000000, 
                  27.000000 34.000000, 35.000000 12.000000))
MULTILINESTRING Z((0.000000 10.000000 1, 0.000000 0.000000 3, 
                   10.000000 0.000000 5))
MULTILINESTRING EMPTY                                                             
MULTILINESTRING EMPTY