ST_LineFromWKB-ApsaraDB RDS(RDS)-阿里云帮助中心

Constructs a LineString geometry object from a Well-Known Binary (WKB) value and an optional spatial reference identifier (SRID).

Syntax

geometry ST_LineFromWKB(bytea WKB);
geometry ST_LineFromWKB(bytea WKB, integer srid);

Parameters

Parameter	Type	Description
WKB	bytea	The WKB representation of the geometry.
srid	integer	The SRID to assign to the geometry object.

Usage notes

If srid is omitted, the default SRID 0 is used.
If the WKB value does not represent a LineString, the function returns NULL.
If the input is confirmed to be a LineString, use ST_GeomFromWKB instead, which is more efficient.

Examples

The following example verifies both the normal return value and the NULL return behavior in a single query.

SELECT
  ST_AsText(ST_LineFromWKB(E'\\x010200000002000000000000000000f03f000000000000004000000000000008400000000000001040')) AS line_result,
  ST_LineFromWKB(E'\\x0101000000000000000000f03f0000000000000040') IS NULL AS null_return;

Expected output:

   line_result    | null_return
-----------------+------------
 LINESTRING(1 2,3 4) | t
(1 row)

The first column confirms a valid LineString is returned from a LineString WKB input. The second column confirms NULL is returned when the input represents a Point, not a LineString.