ST_Buffer

Definición

ST_Buffer toma un objeto de geometría y distancia, y devuelve un objeto de geometría que es la zona de influencia en torno a objeto de origen.

Sintaxis

sde.st_buffer (g1 sde.st_geometry, distance double_precision)

Tipo de devolución

ST_Geometry

Ejemplo

En este ejemplo se crean dos tablas, sensitive_areas y hazardous_sites; rellena las tablas; utiliza ST_Buffer para generar una zona de influencia alrededor de los polígonos en la tabla hazardous_sites; y se encuentra donde las zonas de influencia superpongan los polígonos sensitive_areas.

Oracle

CREATE TABLE sensitive_areas (id integer,                                 zone sde.st_geometry);   CREATE TABLE hazardous_sites (site_id integer,                               name varchar(40),                               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 ( 102, 'W. H. KleenareChemical Repository', sde.st_pointfromtext ('point (60 60)', 0)  );   SELECT sa.id "Sensitive Areas", hs.name "Hazardous Sites" FROM SENSITIVE_AREAS sa, HAZARDOUS_SITES hs WHERE sde.st_overlaps (sa.zone, sde.st_buffer (hs.location, .01)) = 1;

PostgreSQL

CREATE TABLE sensitive_areas (id integer,                                 zone sde.st_geometry);   CREATE TABLE hazardous_sites (site_id integer,                               name varchar(40),                               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 ( 102, 'W. H. KleenareChemical Repository', sde.st_point ('point (60 60)', 0)  );   SELECT sa.id AS "Sensitive Areas", hs.name  AS "Hazardous Sites" FROM sensitive_areas sa, hazardous_sites hs WHERE sde.st_overlaps (sa.zone, sde.st_buffer (hs.location, .01)) = 't';  Sensitive Areas                Hazardous Sites              3                W.H. KleenareChemical Repository