ST_IsEmpty

Definition

ST_IsEmpty returns 1 (Oracle) or t (PostgreSQL) if the ST_Geometry object is empty; otherwise, it returns 0 (Oracle) or f (PostgreSQL).

Syntax

sde.st_isempty (g1 sde.st_geometry)

Return type

Boolean

Example

The CREATE TABLE statement below creates the empty_test table with geotype, which stores the data type of the subclasses that are stored in the g1 ST_Geometry column.

The INSERT statements insert two records for the geometry subclasses point, linestring, and polygon: one that is empty and one that is not.

Oracle

CREATE TABLE empty_test (geotype varchar(20), g1 sde.st_geometry);


INSERT INTO EMPTY_TEST VALUES (
'Point',
sde.st_pointfromtext ('point (10.02 20.01)', 0)
);

INSERT INTO EMPTY_TEST VALUES (
'Point',
sde.st_pointfromtext ('point empty', 0)
);

INSERT INTO EMPTY_TEST VALUES (
'Linestring',
sde.st_linefromtext ('linestring (10.02 20.01, 10.32 23.98, 11.92 25.64)', 0)
);

INSERT INTO EMPTY_TEST VALUES (
'Linestring',
sde.st_linefromtext ('linestring empty', 0)
);

INSERT INTO EMPTY_TEST VALUES (
'Polygon',
sde.st_polyfromtext ('polygon ((10.02 20.01, 11.92 35.64, 25.02 34.15,
19.15 33.94, 10.02 20.01))', 0)
);

PostgreSQL

CREATE TABLE empty_test (geotype varchar(20), g1 sde.st_geometry);

INSERT INTO empty_test VALUES (
'Point',
sde.st_point ('point (10.02 20.01)', 0)
);

INSERT INTO empty_test VALUES (
'Point',
sde.st_point ('point empty', 0)
);

INSERT INTO empty_test VALUES (
'Linestring',
sde.st_linestring ('linestring (10.02 20.01, 10.32 23.98, 11.92 25.64)', 0)
);

INSERT INTO empty_test VALUES (
'Linestring',
sde.st_linestring ('linestring empty', 0)
);

INSERT INTO empty_test VALUES (
'Polygon',
sde.st_polygon ('polygon ((10.02 20.01, 11.92 35.64, 25.02 34.15,
19.15 33.94, 10.02 20.01))', 0)
);

The SELECT query returns the geometry type from the geotype column and the results of the ST_IsEmpty function.

Oracle

SELECT geotype, sde.st_isempty (g1) Is_it_empty
FROM EMPTY_TEST;

GEOTYPE    Is_it_empty

Point         0
Point         1
Linestring    0
Linestring    1
Polygon       1

PostgreSQL

SELECT geotype, sde.st_isempty (g1) AS Is_it_empty
FROM empty_test;

geotype   is_it_empty

Point         f
Point         t
Linestring   f
Linestring    t
Polygon       f