ST_AsEWKB function to return the WKB representation of a geometry or geography object with SRID - ApsaraDB RDS

Returns the Extended Well-Known Binary (EWKB) representation of a geometry or geography object. Unlike standard Well-Known Binary (WKB), the output includes the spatial reference identifier (SRID).

Syntax

bytea  ST_AsEWKB(geometry  g1);
bytea  ST_AsEWKB(geometry  g1 , text  NDRorXDR);
bytea  ST_AsEWKB(geography  g1);
bytea  ST_AsEWKB(geography  g1 , text  NDRorXDR);

Parameters

Parameter	Description
`g1`	The geometry or geography object to serialize.
`NDRorXDR`	The byte order of the output. Valid values: `XDR` (big endian) and `NDR` (little endian). Defaults to `NDR`.

Usage notes

Standard WKB does not include an SRID. Use ST_AsEWKB when the target system requires SRID metadata embedded in the binary output.
Supported geometry types: circular strings, curves, polyhedral surfaces, triangles, triangulated irregular network (TIN) surfaces, and 3D objects.

Examples

Return EWKB with the default little endian byte order:

SELECT ST_AsEWKB(ST_GeomFromText('POLYGON((1 1,1 2,2 2,2 1,1 1))',4326));

Output:

                           st_asewkb
---------------------------------------------------------------
 \x0103000020e61000000100000005000000000000000000f03f000000000.
.000f03f000000000000f03f00000000000000400000000000000040000000.
.00000000400000000000000040000000000000f03f000000000000f03f000.
.000000000f03f
(1 row)

Return EWKB with big endian byte order:

SELECT ST_AsEWKB(ST_GeomFromText('POLYGON((1 1,1 2,2 2,2 1,1 1))',4326),'XDR');

Output:

                           st_asewkb
---------------------------------------------------------------
 \x0020000003000010e600000001000000053ff00000000000003ff000000.
.00000003ff000000000000040000000000000004000000000000000400000.
.000000000040000000000000003ff00000000000003ff00000000000003ff.
.0000000000000
(1 row)