Name
ST_Extract — Extracts a particular type of geometry from a collection and converts them to MULTI*. The values for the type of geometry are 0=Point, 1=Line, 2=Polygon.
Synopsis
geometry ST_Extract(bytea
Geometry, integer
geomDimension);
Description
Extracts a particular type of geometry from a collection and converts them to MULTI*. The values for geomDimension are 0=Point, 1=Line, 2=Polygon
It is similar to applying ST_Dump and then ST_Collect.
Coordinate Dimensions
| 2D | 3D | M |
|---|---|---|
 | | |
Spatial Standards Support
| OGC SFS for SQL. 1.1 (1999) | OGC SFS for SQL. 1.1.0 (2005) | OGC SFS for SQL. 1.2.0 (2006) | SQL-MM Part 3 |
|---|---|---|---|
| - | - | - | - |
Examples
SELECT ST_AsText(ST_Extract(ST_GeomFromText('MULTIPOINT ((1 1), (2 3), (4 1))'),0));
--Result
MULTIPOINT ((1 1), (2 3), (4 1))
SELECT ST_AsText(ST_Extract(ST_GeomFromText(
'GEOMETRYCOLLECTION(GEOMETRYCOLLECTION(LINESTRING (0 0 15, 10 10 25, 20 10 35),POINT(0 0 10)))'
),1));
--Result
MULTILINESTRING ((0 0 15, 10 10 25, 20 10 35))
SELECT ST_AsText(ST_Extract(ST_GeomFromText(
'GEOMETRYCOLLECTION(POLYGON ((0 0 1 1, 10 10 2 2, 10 0 3 3, 0 0 4 4)),POINT(0 0 0 0))'),2));
--Result
MULTIPOLYGON (((0 0 1 1, 10 10 2 2, 10 0 3 3, 0 0 4 4)))