ST_NumPoints

Definition

ST_NumPoints returns the number of points (vertices) in a geometry.

For polygons, both the starting and ending vertices are counted, even though they occupy the same location.

Note that this number is different than the NUMPTS attribute of the ST_Geometry type. The NUMPTS attribute contains a count of the vertices in all the parts of the geometry including separators that occur between parts. There is one separator between each part. For example, a multipart linestring with three parts has two separators. In the NUMPTS attribute, each separator is counted as one vertex. Conversely, the ST_NumPoints function does not include the separators in the vertex count.

Syntax

Oracle and PostgreSQL

sde.st_numpoints (geometry1 sde.st_geometry)

SQLite

st_numpoints (geometry1 geometryblob)

Return type

Integer

Example

The numpoints_test table is created with the geotype column, which contains the geometry type stored in the g1 column.

The INSERT statements insert a point, a linestring, and a polygon.

The SELECT query uses the ST_NumPoints function to get the number of points in each feature for each feature type.

Oracle

CREATE TABLE numpoints_test (
 geotype varchar(12),
 g1 sde.st_geometry
);

INSERT INTO NUMPOINTS_TEST VALUES (
 'point',
 sde.st_pointfromtext ('point (10.02 20.01)', 4326)
);

INSERT INTO NUMPOINTS_TEST VALUES (
 'linestring',
 sde.st_linefromtext ('linestring (10.02 20.01, 23.73 21.92)', 4326)
);

INSERT INTO NUMPOINTS_TEST VALUES (
 'polygon',
 sde.st_polyfromtext ('polygon ((10.02 20.01, 23.73 21.92, 24.51 12.98, 11.64 13.42, 10.02 20.01))', 4326)
);

SELECT geotype, sde.st_numpoints (g1) Number_of_points
 FROM NUMPOINTS_TEST;

GEOTYPE     Number_of_points

point                       1
linestring                  2
polygon                     5

PostgreSQL

CREATE TABLE numpoints_test (
 geotype varchar(12),
 g1 sde.st_geometry
);

INSERT INTO numpoints_test VALUES (
 'point',
 sde.st_point ('point (10.02 20.01)', 4326)
);

INSERT INTO numpoints_test VALUES (
 'linestring',
 sde.st_linestring ('linestring (10.02 20.01, 23.73 21.92)', 4326)
);

INSERT INTO numpoints_test VALUES (
 'polygon',
 sde.st_polygon ('polygon ((10.02 20.01, 23.73 21.92, 24.51 12.98, 11.64 13.42, 10.02 20.01))', 4326)
);

SELECT geotype, sde.st_numpoints (g1)
 AS Number_of_points
 FROM numpoints_test;

geotype     number_of_points

point                       1
linestring                  2
polygon                     5

SQLite

CREATE TABLE numpoints_test (
 geotype text(12)
);

SELECT AddGeometryColumn(
 NULL,
 'numpoints_test',
 'g1',
 4326,
 'geometry',
 'xy',
 'null'
);

INSERT INTO numpoints_test VALUES (
 'point',
 st_point ('point (10.02 20.01)', 4326)
);

INSERT INTO numpoints_test VALUES (
 'linestring',
 st_linestring ('linestring (10.02 20.01, 23.73 21.92)', 4326)
);

INSERT INTO numpoints_test VALUES (
 'polygon',
 st_polygon ('polygon ((10.02 20.01, 23.73 21.92, 24.51 12.98, 11.64 13.42, 10.02 20.01))', 4326)
);

SELECT geotype AS "Type of geometry", st_numpoints (g1) AS "Number of points"
 FROM numpoints_test;

Type of geometry     Number of points

point                       1
linestring                  2
polygon                     5