ST_PolyFromText function

The ST_PolyFromText function takes a well-known text representation of a polygon and, optionally, a spatial reference system identifier as input parameters and returns the corresponding polygon.

If the given well-known text representation is null, then null is returned.

The recommended function for achieving the same result is the ST_Polygon function. It is recommended because of its flexibility: ST_Polygon takes additional forms of input as well as the well-known text representation.

Syntax

Parameters

wkt

A value of type CLOB(2G) that contains the well-known text representation of the resulting polygon.

srs_id

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

If the srs_id parameter is omitted, the spatial reference system with the numeric identifier 0 (zero) is used.

If 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_Polygon

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.

This example illustrates how ST_PolyFromText can be used to create and insert a polygon from its well-known text representation. The record that is inserted has ID = 1110, and the geometry is a polygon in spatial reference system 1. The polygon is in the well-known text representation of a polygon. The X and Y coordinates for this geometry are: (50, 20) (50, 40) (70, 30).


SET CURRENT FUNCTION PATH = CURRENT FUNCTION PATH, db2gse
CREATE TABLE sample_polys (id INTEGER, geometry ST_Polygon)

INSERT INTO sample_polys
  VALUES (1110, ST_PolyFromText ('polygon ((50 20, 50 40, 70 30, 50 20))', 1) )

The following SELECT statement returns the polygon that was recorded in the table:


SELECT id, CAST( ST_AsText( geometry ) AS VARCHAR(120) ) POLYGON
  FROM sample_polys
  WHERE id = 1110

Results:


ID         POLYGON
---------- --------------------------------------------------------------------
      1110 POLYGON (( 50.00000000 20.00000000, 70.00000000 30.00000000,
                      50.00000000 40.00000000, 50.00000000 20.00000000))