ST_StartPoint

Definition

ST_StartPoint returns the first point of a linestring.

Syntax

Oracle and PostgreSQL

sde.st_startpoint (ln1 sde.st_geometry)

SQLite

st_startpoint (ln1 geometryblob)

Return type

ST_Point

Examples

The startpoint_test table is created with the gid integer column, which uniquely identifies the rows of the table, and the ln1 ST_LineString column.

The INSERT statements insert the ST_LineStrings into the ln1 column. The first ST_LineString does not have z-coordinates or measures, while the second ST_LineString has both.

The ST_StartPoint function extracts the first point of each ST_LineString. The first point in the list does not have a z-coordinate or measure, while the second point has both, because the source linestring does.

Oracle

CREATE TABLE startpoint_test (
 gid integer,
 ln1 sde.st_geometry
);

INSERT INTO STARTPOINT_TEST VALUES (
 1,
 sde.st_linefromtext ('linestring (10.02 20.01, 23.73 21.92, 30.10 40.23)', 4326)
);

INSERT INTO STARTPOINT_TEST VALUES (
 2,
 sde.st_linefromtext ('linestring zm(10.02 20.01 5 7, 23.73 21.92 6.5 7.1, 30.10 40.23 6.9 7.2)', 4326)
);

SELECT gid, sde.st_astext (sde.st_startpoint (ln1)) Startpoint
 FROM STARTPOINT_TEST;

GID  Startpoint

1    POINT (10.02000000 20.01000000)
2    POINT ZM (10.02000000 20.01000000 5.00000000 7.00000000)

PostgreSQL

CREATE TABLE startpoint_test (
 gid serial,
 ln1 sde.st_geometry
);

INSERT INTO startpoint_test (ln1) VALUES (
 sde.st_linestring ('linestring (10.02 20.01, 23.73 21.92, 30.10 40.23)', 4326)
);

INSERT INTO startpoint_test (ln1) VALUES (
 sde.st_linestring ('linestring zm(10.02 20.01 5 7, 23.73 21.92 6.5 7.1, 30.10 40.23 6.9 7.2)', 4326)
);

SELECT gid, sde.st_astext (sde.st_startpoint (ln1)) 
 AS Startpoint
 FROM startpoint_test;

gid  startpoint

1    POINT (10.02000000 20.01000000)
2    POINT ZM (10.02000000 20.01000000 5.00000000 7.00000000)

SQLite

CREATE TABLE startpoint_test (
 gid integer primary key autoincrement not null
);

SELECT AddGeometryColumn(
 NULL,
 'startpoint_test',
 'ln1',
 4326,
 'linestringzm',
 'xyzm',
 'null'
);

INSERT INTO startpoint_test (ln1) VALUES (
 st_linestring ('linestring (10.02 20.01, 23.73 21.92, 30.10 40.23)', 4326)
);

INSERT INTO startpoint_test(ln1) VALUES (
 st_linestring ('linestring zm(10.02 20.01 5 7, 23.73 21.92 6.5 7.1, 30.10 40.23 6.9 7.2)', 4326)
);

SELECT gid, st_astext (st_startpoint (ln1)) 
 AS "Startpoint"
 FROM startpoint_test;

gid  Startpoint

1    POINT (10.02000000 20.01000000)
2    POINT ZM (10.02000000 20.01000000 5.00000000 7.00000000)