Returns the Extended Well-Known Binary (EWKB) representation of a geometry or geography object. Unlike standard Well-Known Binary (WKB), the returned value includes the spatial reference identifier (SRID) of the input object.
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 convert. |
NDRorXDR | The byte order of the output. Valid values: XDR (big-endian) and NDR (little-endian). Default value: NDR. |
Usage notes
The WKB specification defines that standard WKB output does not include SRIDs. Use
ST_AsEWKBwhen you need the SRID embedded in the binary output.Supported geometry types include 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)