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Returns a homogeneous multi-geometry from a given geometry collection. The type numbers are:
  1. POINT
  2. LINESTRING
  3. POLYGON
If the type parameter is omitted a multi-geometry of the highest dimension is returned. ST_CollectionExtract

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Signatures

ST_CollectionExtract (A: Geometry)

ST_CollectionExtract (A: Geometry, type: Integer)

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Parameters

​
A
Geometry
required
The input geometry.
​
type
Integer
The output type.

​
Return type

The resulting geometry.

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Example

WITH test_data as (
    ST_GeomFromText(
        'GEOMETRYCOLLECTION(POINT(40 10), POLYGON((0 0, 0 5, 5 5, 5 0, 0 0)))'
    ) as geom
)
SELECT ST_CollectionExtract(geom) as c1, ST_CollectionExtract(geom, 1) as c2
FROM test_data


+----------------------------------------------------------------------------+
|c1                                        |c2                               |
+----------------------------------------------------------------------------+
|MULTIPOLYGON(((0 0, 0 5, 5 5, 5 0, 0 0))) |MULTIPOINT(40 10)                |              |
+----------------------------------------------------------------------------+