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