Categories:

Geospatial functions

ST_ASGEOJSON

Given a value of type GEOGRAPHY or GEOMETRY, return the GeoJSON representation of that value.

Syntax

ST_ASGEOJSON( <geography_or_geometry_expression> )

Arguments

geography_or_geometry_expression

The argument must be an expression of type GEOGRAPHY or GEOMETRY.

Returns

An OBJECT in GeoJSON format.

Usage notes

For GEOMETRY objects:

  • The returned GEOMETRY object uses the same coordinate system as the input GEOMETRY object.

    Note that the GeoJSON specification requires that geometry be in the WGS84 coordinate system (SRID = 4326). However, the ST_ASGEOJSON function does not enforce this.

  • The function does not add the SRID or any other CRS information to the output.

Examples

GEOGRAPHY examples

The following example demonstrates the ST_ASGEOJSON function:

create table geospatial_table (id INTEGER, g GEOGRAPHY);
insert into geospatial_table values
    (1, 'POINT(-122.35 37.55)'), (2, 'LINESTRING(-124.20 42.00, -120.01 41.99)');

select st_asgeojson(g)
    from geospatial_table
    order by id;
+------------------------+
| ST_ASGEOJSON(G)        |
|------------------------|
| {                      |
|   "coordinates": [     |
|     -122.35,           |
|     37.55              |
|   ],                   |
|   "type": "Point"      |
| }                      |
| {                      |
|   "coordinates": [     |
|     [                  |
|       -124.2,          |
|       42               |
|     ],                 |
|     [                  |
|       -120.01,         |
|       41.99            |
|     ]                  |
|   ],                   |
|   "type": "LineString" |
| }                      |
+------------------------+

Casting the VARIANT output to VARCHAR results in the following:

select st_asgeojson(g)::varchar
    from geospatial_table
    order by id;
+-------------------------------------------------------------------+
| ST_ASGEOJSON(G)::VARCHAR                                          |
|-------------------------------------------------------------------|
| {"coordinates":[-122.35,37.55],"type":"Point"}                    |
| {"coordinates":[[-124.2,42],[-120.01,41.99]],"type":"LineString"} |
+-------------------------------------------------------------------+

GEOMETRY examples

The following example demonstrates the ST_ASGEOJSON function with a GEOMETRY object as input:

SELECT ST_ASGEOJSON(TO_GEOMETRY('SRID=4326;LINESTRING(389866 5819003, 390000 5830000)')) AS geojson;

+------------------------+
| GEOJSON                |
|------------------------|
|{                       |
|  "coordinates": [      |
|    [                   |
|      389866,           |
|      5819003           |
|    ],                  |
|    [                   |
|      390000,           |
|      5830000           |
|    ]                   |
|  ],                    |
|  "type": "LineString"  |
|}                       |
+------------------------+