ST_StartPoint — Returns the first point of a LINESTRING geometry as a POINT.


geometry ST_StartPoint(geometry geomA);


Returns the first point of a LINESTRING geometry as a POINT or NULL if the input parameter is not a LINESTRING.

This method implements the SQL/MM specification. SQL-MM 3: 7.1.3

This function supports 3d and will not drop the z-index.


Changed: 2.0.0 no longer works with single geometry multilinestrings. In older versions of PostGIS -- a single line multilinestring would work happily with this function and return the start point. In 2.0.0 it just returns NULL like any other multilinestring. The older behavior was an undocumented feature, but people who assumed they had their data stored as LINESTRING may experience these returning NULL in 2.0 now.


SELECT ST_AsText(ST_StartPoint('LINESTRING(0 1, 0 2)'::geometry));
 POINT(0 1)
(1 row)

SELECT ST_StartPoint('POINT(0 1)'::geometry) IS NULL AS is_null;
(1 row)

--3d line
SELECT ST_AsEWKT(ST_StartPoint('LINESTRING(0 1 1, 0 2 2)'::geometry));
 POINT(0 1 1)
(1 row)

See Also

ST_EndPoint, ST_PointN