ST_GeomCollFromWKB function

The ST_GeomCollFromWKB function takes a well-known binary (WKB) format of a geometry collection and, optionally, a spatial reference system identifier as input parameters and returns the corresponding geometry collection.

If the specified WKB format is null, then null is returned.

The preferred version for this functionality is ST_GeomCollection.

Syntax

Parameter

wkb

A value of type BLOB(2G) that contains the well-known binary format of the resulting geometry collection.

srs_id

A value of type INTEGER that identifies the spatial reference system for the resulting geometry collection.

If the srs_id parameter is omitted, the spatial reference system with the numeric identifier 4326 is used implicitly.

If srs_id does not identify a spatial reference system listed in the catalog view SYSGEO.ST_SPATIAL_REFERENCE_SYSTEMS, then an error is returned (SQLSTATE 38SU1).

Return type

ST_GeomCollection

Example

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

The following code illustrates how the ST_GeomCollFromWKB function can be used to create and query the coordinates of a geometry collection in a well-known binary format. The rows are inserted into the SAMPLE_GEOMCOLLECTION table with IDs 4021 and 4022 and geometry collections in spatial reference system 1.


CREATE TABLE sample_geomcollections(id INTEGER, 
  geometry ST_GEOMCOLLECTION, wkb varbinary(32000))

INSERT INTO sample_geomcollections(id, geometry)
VALUES
  (4021, ST_GeomCollFromTxt('multipoint(1 2, 4 3, 5 6)', 1)),
  (4022, ST_GeomCollFromTxt('multilinestring(
                           (33 2, 34 3, 35 6),
                           (28 4, 29 5, 31 8, 43 12))', 1))

UPDATE sample_geomcollections AS temp_correlated
SET    wkb = ST_AsBinary(geometry)
WHERE  id = temp_correlated.id
 
SELECT id, cast(ST_AsText(ST_GeomCollFromWKB(wkb,1)) AS varchar(190)) 
           AS GeomCollection
FROM   sample_geomcollections

Results:


ID          GEOMCOLLECTION
----------- -----------------------------------------------------
       4021 MULTIPOINT (1.000000 2.000000, 4.000000 3.000000, 
              5.000000 6.000000)                                                                                    
       4022 MULTILINESTRING ((33.000000 2.000000, 34.000000 3.000000, 
              35.000000 6.000000),(28.000000 4.000000, 29.000000 
              5.000000, 31.000000 8.000000, 43.000000 12.000000))