ST_Overlaps

Definition

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

Syntax

sde.st_overlaps (g1 sde.st_geometry, g2 sde.st_geometry)

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 zone 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 location point column.

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

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


INSERT INTO sensitive_areas VALUES (
1,
sde.st_polygon ('polygon ((20 30, 30 30, 30 40, 20 40, 20 30))', 0)
);

INSERT INTO sensitive_areas VALUES (
2,
sde.st_polygon ('polygon ((30 30, 30 50, 50 50, 50 30, 30 30))', 0)
);

INSERT INTO sensitive_areas VALUES (
3,
sde.st_polygon ('polygon ((40 40, 40 60, 60 60, 60 40, 40 40))', 0)
);

INSERT INTO hazardous_sites VALUES (
4,
sde.st_point ('point (60 60)', 0)
);

INSERT INTO hazardous_sites VALUES (
5,
sde.st_point ('point (30 30)', 0)
);

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 zone polygons that overlap the buffered radius of the hazardous_sites location points.

Oracle

SELECT UNIQUE (hs.id)
FROM HAZARDOUS_SITES hs, SENSITIVE_AREAS sa
WHERE sde.st_overlaps (sde.st_buffer (hs.location, .01), sa.zone) = 1;

ID

4
5

PostgreSQL

SELECT DISTINCT (hs.id)
FROM hazardous_sites hs, sensitive_areas sa
WHERE sde.st_overlaps (sde.st_buffer (hs.location, .01), sa.zone) = 't';

ID

4
5