ST_Overlaps

Definition

ST_Overlaps takes two geometry objects and returns 1 (Oracle and SQLite) or t (PostgreSQL) if the intersection of the objects results in a geometry object of the same dimension but not equal to either source object; otherwise, it returns 0 (Oracle and SQLite) or f (PostgreSQL).

Syntax

Oracle and PostgreSQL

sde.st_overlaps (geometry1 sde.st_geometry, geometry2 sde.st_geometry)

SQLite

st_overlaps (geometry1 geometryblob, geometry2 geometryblob)

Return type

Boolean

Example

The county supervisor needs a list of sensitive areas that overlap the buffered radius of hazardous waste sites. The sensitive_areas table contains several columns that describe the threatened institutions in addition to the shape column, which stores the institutions' ST_Polygon geometries.

The hazardous_sites table stores the identity of the sites in the id column, while the actual geographic location of each site is stored in the site point column.

The sensitive_areas and hazardous_sites tables are joined by the ST_Overlaps function, which returns the ID for all sensitive_areas rows that contain polygons that overlap the buffered radius of the hazardous_sites points.

Oracle

CREATE TABLE sensitive_areas (
 id integer, 
 shape sde.st_geometry
); 

CREATE TABLE hazardous_sites (
 id integer,
 site sde.st_geometry
);


INSERT INTO sensitive_areas VALUES (
 1,
 sde.st_geometry ('polygon ((.20 .30, .30 .30, .30 .40, .20 .40, .20 .30))', 4326)
);

INSERT INTO sensitive_areas VALUES (
 2,
 sde.st_geometry ('polygon ((.30 .30, .30 .50, .50 .50, .50 .30, .30 .30))', 4326)
);

INSERT INTO sensitive_areas VALUES (
 3,
 sde.st_geometry ('polygon ((.40 .40, .40 .60, .60 .60, .60 .40, .40 .40))', 4326)
);

INSERT INTO hazardous_sites VALUES (
 4,
 sde.st_geometry ('point (.60 .60)', 4326)
);

INSERT INTO hazardous_sites VALUES (
 5,
 sde.st_geometry ('point (.30 .30)', 4326)
);
SELECT UNIQUE (hs.id)
 FROM HAZARDOUS_SITES hs, SENSITIVE_AREAS sa
 WHERE sde.st_overlaps (sde.st_buffer (hs.site, .001), sa.shape) = 1;

ID

4
5

PostgreSQL

CREATE TABLE sensitive_areas (
 id serial, 
 shape sde.st_geometry
); 

CREATE TABLE hazardous_sites (
 id serial,
 site sde.st_geometry
);


INSERT INTO sensitive_areas (shape) VALUES (
 sde.st_geometry ('polygon ((.20 .30, .30 .30, .30 .40, .20 .40, .20 .30))', 4326)
);

INSERT INTO sensitive_areas (shape) VALUES (
 sde.st_geometry ('polygon ((.30 .30, .30 .50, .50 .50, .50 .30, .30 .30))', 4326)
);

INSERT INTO sensitive_areas (shape) VALUES (
 sde.st_geometry ('polygon ((.40 .40, .40 .60, .60 .60, .60 .40, .40 .40))', 4326)
);

INSERT INTO hazardous_sites (site) VALUES (
 sde.st_geometry ('point (.60 .60)', 4326)
);

INSERT INTO hazardous_sites (site) VALUES (
 sde.st_geometry ('point (.30 .30)', 4326)
);
SELECT DISTINCT (hs.id) AS "Hazardous Site ID"
 FROM hazardous_sites hs, sensitive_areas sa
 WHERE sde.st_overlaps (sde.st_buffer (hs.site, .001), sa.shape) = 't';

id

1
2

SQLite

CREATE TABLE sensitive_areas (
 id integer primary key autoincrement not null
); 

SELECT AddGeometryColumn(
 NULL,
 'sensitive_areas',
 'shape',
 4326,
 'polygon',
 'xy',
 'null'
);

CREATE TABLE hazardous_sites (
 id integer primary key autoincrement not null,
 site_name varchar(30)
);

SELECT AddGeometryColumn(
 NULL,
 'hazardous_sites',
 'site',
 4326,
 'point',
 'xy',
 'null'
);

INSERT INTO sensitive_areas (shape) VALUES (
 st_geometry ('polygon ((.20 .30, .30 .30, .30 .40, .20 .40, .20 .30))', 4326)
);

INSERT INTO sensitive_areas (shape) VALUES (
 st_geometry ('polygon ((.30 .30, .30 .50, .50 .50, .50 .30, .30 .30))', 4326)
);

INSERT INTO sensitive_areas (shape) VALUES (
 st_geometry ('polygon ((.40 .40, .40 .60, .60 .60, .60 .40, .40 .40))', 4326)
);

INSERT INTO hazardous_sites (site_name, site) VALUES (
 'Kemlabs',
 st_geometry ('point (.60 .60)', 4326)
);

INSERT INTO hazardous_sites (site_name, site) VALUES (
 'Medi-Waste',
 st_geometry ('point (.30 .30)', 4326)
);
SELECT DISTINCT (hs.site_name) AS "Hazardous Site"
 FROM hazardous_sites hs, sensitive_areas sa
 WHERE st_overlaps (st_buffer (hs.site, .001), sa.shape) = 1;

Hazardous Site

Kemlabs
Medi-Waste

Related Topics

6/19/2015