ST_TOMULTIPOLYGON scalar function

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The ST_TOMULTIPOLYGON function takes a geometry as an input parameter and converts it to a multipolygon.

The specified geometry must be a polygon or a multipolygon.

If geometry is null, the result is the null value. An empty multipolygon is not supported.

geometry: A value of type ST_GEOMETRY or one of its subtypes that represents the geometry that is converted to a multipolygon.; A geometry can be converted to a multipolygon if it is a polygon or a multipolygon. If the conversion cannot be performed, then an exception condition is raised.

The result of the function is ST_MULTIPOLYGON.

Example

This example creates several geometries and then uses ST_TOMULTIPOLYGON to return multipolygons.

CREATE TABLE sample_geometries (id INTEGER, geometry QSYS2.ST_GEOMETRY);
CREATE TABLE sample_multipolygons (id INTEGER, multipolygon QSYS2.ST_MULTIPOLYGON);

INSERT INTO sample_geometries
  VALUES (1, QSYS2.ST_MULTIPOLYGON('multipolygon (((0 0, 0 4, 5 4, 5 0, 0 0)),
                                               ((10 10, 10 15, 13 17, 10 10)))')),
         (2, QSYS2.ST_POLYGON('polygon ((0 0, 0 4, 5 4, 5 0, 0 0))'));

INSERT INTO sample_multipolygons 
 (SELECT ID, QSYS2.ST_TOMULTIPOLYGON(geometry)
   FROM sample_geometries);
   
SELECT id, QSYS2.ST_ASTEXT(multipolygon) AS multipolygons FROM sample_multipolygons;

Results:


ID        MULTIPOLYGONS
-------   ------------------------------------------------------------------------
      1   MULTIPOLYGON (((10.0 10.0, 13.0 17.0, 10.0 15.0, 10.0 10.0)), 
                        ((0.0 0.0, 5.0 0.0, 5.0 4.0, 0.0 4.0, 0.0 0.0))) 
      2   MULTIPOLYGON (((0.0 0.0, 5.0 0.0, 5.0 4.0, 0.0 4.0, 0.0 0.0)))