ST_MPolyFromWKB function
The ST_MPolyFromWKB function takes a well-known binary representation of a multipolygon and, optionally, a spatial reference system identifier as input parameters and returns the corresponding multipolygon.
If the given well-known binary representation is null, then null is returned.
The recommended function for achieving the same result is the ST_MultiPolygon function. It is recommended because of its flexibility: ST_MultiPolygon takes additional forms of input as well as the well-known binary representation.
Syntax
Parameters
- wkb
- A value of type BLOB(2G) that contains the well-known binary representation of the resulting multipolygon.
- srs_id
- A value of type INTEGER that identifies the spatial reference
system for the resulting multipolygon.
If the srs_id parameter is omitted, the spatial reference system with the numeric identifier 0 (zero) is used.
If the specified srs_id does not identify a spatial reference system listed in the catalog view DB2GSE.ST_SPATIAL_REFERENCE_SYSTEMS, then an exception condition is raised (SQLSTATE 38SU1).
Return type
db2gse.ST_MultiPolygon
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.
- Polygon 1: (1, 72) (4, 79) (5, 76) (1, 72)
- Polygon 2: (10, 20) (10, 40) (30, 41) (10, 20)
- Polygon 3: (9, 43) (7, 44) (6, 47) (9, 43)
SET CURRENT FUNCTION PATH = CURRENT FUNCTION PATH, db2gse
CREATE TABLE sample_mpolys (id INTEGER,
geometry ST_MultiPolygon, wkb BLOB(32K))
INSERT INTO sample_mpolys
VALUES (10, ST_MultiPolygon ('multipolygon
(( (1 72, 4 79, 5 76, 1 72),
(10 20, 10 40, 30 41, 10 20),
(9 43, 7 44, 6 47, 9 43) ))', 1))
UPDATE sample_mpolys AS temporary_correlated
SET wkb = ST_AsBinary( geometry )
WHERE id = temporary_correlated.id
In the following SELECT statement, the ST_MPolyFromWKB
function is used to retrieve the multipolygon from the WKB column.
SELECT id, CAST( ST_AsText( ST_MPolyFromWKB (wkb) )
AS VARCHAR(320) ) MULTIPOLYGON
FROM sample_mpolys
WHERE id = 10
Results:
ID MULTIPOLYGON
---------- --------------------------------------------------------------------
10 MULTIPOLYGON ((( 10.00000000 20.00000000, 30.00000000
41.00000000, 10.00000000 40.00000000, 10.00000000
20.00000000)),
( 1.00000000 72.00000000, 5.00000000
76.00000000, 4.00000000 79.0000000, 1.00000000
72,00000000)),
( 9.00000000 43.00000000, 6.00000000
47.00000000, 7.00000000 44.00000000, 9.00000000
43.00000000 )))