The ST_AsText() function

The ST_AsText() function takes an ST_Geometry object and returns its well-known text representation.

The return type of ST_AsText() is defined as ST_Geometry to allow spatial objects greater than 2 kilobytes to be retrieved by a client application.

Typically, you use ST_AsText() to retrieve spatial data from the server and send it to a client, as in:

SELECT ST_AsText(geomcol) FROM mytable

HCL OneDB™ automatically casts the output of the ST_AsText() function to the proper data type for transmission to the client.

You can write user-defined routines (UDRs) in C or SPL to extend the functionality of the existing spatial data type functions. You can use ST_AsText() to convert an ST_Geometry to its well-known text representation. If you pass the output of ST_AsText() to another UDR whose function signature requires an LVARCHAR input, you should explicitly cast the return type of ST_AsText() to LVARCHAR, as in:

EXECUTE FUNCTION MySpatialFunc(ST_AsText(geomcol)::lvarchar)

Syntax

ST_AsText(g1 ST_Geometry)

Return type

ST_Geometry

Example

The ST_AsText() function converts the hazardous_sites location point into its text description:

CREATE TABLE hazardous_sites (site_id   integer,
                              name      varchar(40),
                              location  ST_Point);



INSERT INTO hazardous_sites VALUES(
     102, 'W. H. Kleenare Chemical Repository',
     ST_PointFromText('point (1020.12 324.02)',1000)
);
SELECT site_id, name, ST_AsText(location) Location
   FROM hazardous_sites;


site_id   102
name      W. H. Kleenare Chemical Repository
location  POINT (1020.12 324.02)