convert Postgres geometry format to WKT - sql

Question

I have a Postgres table which stores polygon geometry in its specific format in one of the column, something like this-
0103000020E61000000100000004000000B8627F336B1554405DD602FFA2733A40B8627FA7601554403851F8EBC7723A40B8627FC38F15544036D539E90B733A40B8627F336B1554405DD602FFA2733A40
I know how to convert this single value to WKT using ST_AsText which will give me POLYGON((Lat Long)). But I want to convert whole column into WKT format.
How to achieve this?
Thanks!

Answer 1

Have you tried this?
SELECT ST_AsText(your_geom_column) FROM your_table
In the following examples I'll show you a few ways to serialise your geometries. Here is sample data with two points encoded as 4326 (WGS84):
CREATE TEMPORARY TABLE tmp
(geom GEOMETRY);
INSERT INTO tmp VALUES
('SRID=4326;POINT(1 2)'),
('SRID=4326;POINT(2 4)');
Geometries as WKB (Well-Known Binary, default):
SELECT geom FROM tmp;
geom
----------------------------------------------------
0101000020E6100000000000000000F03F0000000000000040
0101000020E610000000000000000000400000000000001040
Geometries as WKT (Well-Known Text) and EWKT (WKT with an explicit Spatial Reference System):
SELECT ST_AsText(geom), ST_AsEWKT(geom) FROM tmp;
st_astext | st_asewkt
------------+----------------------
POINT(1 2) | SRID=4326;POINT(1 2)
POINT(2 4) | SRID=4326;POINT(2 4)
In case you fancy GeoJSON
SELECT ST_AsGeoJSON(geom) FROM tmp;
st_asgeojson
--------------------------------------
{"type":"Point","coordinates":[1,2]}
{"type":"Point","coordinates":[2,4]}
Or even GML
SELECT ST_AsGML(geom) FROM tmp;
st_asgml
-----------------------------------------------------------------------------------
<gml:Point srsName="EPSG:4326"><gml:coordinates>1,2</gml:coordinates></gml:Point>
<gml:Point srsName="EPSG:4326"><gml:coordinates>2,4</gml:coordinates></gml:Point>
The Google Earth enthusiasts also have their fun! Geometries as KML
SELECT ST_AsKML(geom) FROM tmp;
st_askml
-----------------------------------------------
<Point><coordinates>1,2</coordinates></Point>
<Point><coordinates>2,4</coordinates></Point>
Librarians might also wanna take a look at ST_AsMARC21 (added in 3.3)
SELECT ST_AsMARC21(geom) FROM tmp;
st_asmarc21
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
<record xmlns="http://www.loc.gov/MARC21/slim"><datafield tag="034" ind1="1" ind2=" "><subfield code="a">a</subfield><subfield code="d">E0010000</subfield><subfield code="e">E0010000</subfield><subfield code="f">N0020000</subfield><subfield code="g">N0020000</subfield></dataf
ield></record>
<record xmlns="http://www.loc.gov/MARC21/slim"><datafield tag="034" ind1="1" ind2=" "><subfield code="a">a</subfield><subfield code="d">E0020000</subfield><subfield code="e">E0020000</subfield><subfield code="f">N0040000</subfield><subfield code="g">N0040000</subfield></dataf
ield></record>
(2 rows)
And the list goes on! In the PostGIS documentation there are other fancy ways to serialise geometry.
Demo: db<>fiddle