ST_Intersection

Definición

ST_Intersection toma dos objetos de geometría y devuelve el conjunto de intersección como un objeto de geometría bidimensional.

Sintaxis

Oracle y PostgreSQL

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

SQLite

st_intersection (geometry1 geometryblob, geometry2 geometryblob)

Tipo de devolución

Oracle y PostgreSQL

ST_Geometry

SQLite

Geometryblob

Ejemplo

El jefe de bomberos debe obtener las áreas de los hospitales, escuelas y centros de asistencia intersecados por el radio de una posible contaminación de los residuos peligrosos.

Los hospitales, las escuelas y los centros de asistencia se almacenan en la tabla population creada con la declaración CREATE TABLE que se muestra a continuación. La columna de forma, que se define como un polígono, almacena el contorno de cada una de las zonas sensibles.

Los emplazamientos peligrosos se almacenan en la tabla waste_sites creada con la declaración CREATE TABLE siguiente. La columna de sitio, que se define como un punto, almacena una ubicación que es el centro geográfico de cada sitio peligroso.

La función ST_Buffer genera una zona de influencia que rodea los sitios de residuos peligrosos. La función ST_Intersection genera polígonos desde la intersección de las áreas sensibles y sitios de residuos peligrosos de la zona de influencia.

Oracle

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

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


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

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

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

INSERT INTO waste_sites VALUES (
 40,
 sde.st_geometry ('point (.60 .60)', 4326)
);

INSERT INTO waste_sites VALUES (
 50,
 sde.st_geometry ('point (.30 .30)', 4326)
);

SELECT sa.id, sde.st_astext (sde.st_intersection (sde.st_buffer (hs.site, .1), sa.shape)) Intersection
 FROM population sa, waste_sites hs
 WHERE hs.id = 50
 AND sde.st_astext (sde.st_intersection (sde.st_buffer (hs.site, .01), sa.shape)) 
 NOT LIKE '%EMPTY%';

  ID  INTERSECTION

1     POLYGON (( 0.29000000 0.30000000, 0.30000000 0.30000000, 0.30000000
0.31000000, 0.29934597 0.30997859, 0.29869474 0.30991445, 0.29804910 0.30980785,
 0.29741181 0.30965926, 0.29678561 0.30946930, 0.29617317 0.30923880, 0.29557711
 0.30896873, 0.29500000 0.30866025, 0.29444430 0.30831470, 0.29391239 0.30793353
, 0.29340654 0.30751840, 0.29292893 0.30707107, 0.29248160 0.30659346, 0.2920664
7 0.30608761, 0.29168530 0.30555570, 0.29133975 0.30500000, 0.29103127 0.3044228
9, 0.29076121 0.30382683, 0.29053070 0.30321440, 0.29034074 0.30258819, 0.290192
15 0.30195090, 0.29008555 0.30130526, 0.29002141 0.30065403, 0.29000000 0.300000
00))

2     POLYGON (( 0.30000000 0.30000000, 0.31000000 0.30000000, 0.30997859
0.30065403, 0.30991445 0.30130526, 0.30980785 0.30195090, 0.30965926 0.30258819,
 0.30946930 0.30321440, 0.30923880 0.30382683, 0.30896873 0.30442289, 0.30866025
 0.30500000, 0.30831470 0.30555570, 0.30793353 0.30608761, 0.30751840 0.30659346
, 0.30707107 0.30707107, 0.30659346 0.30751840, 0.30608761 0.30793353, 0.3055557
0 0.30831470, 0.30500000 0.30866025, 0.30442289 0.30896873, 0.30382683 0.3092388
0, 0.30321440 0.30946930, 0.30258819 0.30965926, 0.30195090 0.30980785, 0.301305
26 0.30991445, 0.30065403 0.30997859, 0.30000000 0.31000000, 0.30000000 0.300000
00))

PostgreSQL

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

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


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

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

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

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

INSERT INTO waste_sites (site) VALUES (
 sde.st_geometry ('point (.30 .30)', 4326)
);

--Replace hs.id with ID value of second record in waste_sites table if not 2.
SELECT sa.id, sde.st_astext (sde.st_intersection (sde.st_buffer (hs.site, .01), sa.shape))
 AS Intersection
 FROM population sa, waste_sites hs
 WHERE hs.id = 2
 AND sde.st_astext (sde.st_intersection (sde.st_buffer (hs.site, .1), sa.shape))::varchar 
 NOT LIKE '%EMPTY%';

  id  intersection

1      POLYGON (( 0.29000000 0.30000000, 0.30000000 0.30000000, 0.30000000
0.31000000, 0.29934597 0.30997859, 0.29869474 0.30991445, 0.29804910 0.30980785,
 0.29741181 0.30965926, 0.29678561 0.30946930, 0.29617317 0.30923880, 0.29557711
 0.30896873, 0.29500000 0.30866025, 0.29444430 0.30831470, 0.29391239 0.30793353
, 0.29340654 0.30751840, 0.29292893 0.30707107, 0.29248160 0.30659346, 0.2920664
7 0.30608761, 0.29168530 0.30555570, 0.29133975 0.30500000, 0.29103127 0.3044228
9, 0.29076121 0.30382683, 0.29053070 0.30321440, 0.29034074 0.30258819, 0.290192
15 0.30195090, 0.29008555 0.30130526, 0.29002141 0.30065403, 0.29000000 0.300000
00))

2      POLYGON (( 0.30000000 0.30000000, 0.31000000 0.30000000, 0.30997859
0.30065403, 0.30991445 0.30130526, 0.30980785 0.30195090, 0.30965926 0.30258819,
 0.30946930 0.30321440, 0.30923880 0.30382683, 0.30896873 0.30442289, 0.30866025
 0.30500000, 0.30831470 0.30555570, 0.30793353 0.30608761, 0.30751840 0.30659346
, 0.30707107 0.30707107, 0.30659346 0.30751840, 0.30608761 0.30793353, 0.3055557
0 0.30831470, 0.30500000 0.30866025, 0.30442289 0.30896873, 0.30382683 0.3092388
0, 0.30321440 0.30946930, 0.30258819 0.30965926, 0.30195090 0.30980785, 0.301305
26 0.30991445, 0.30065403 0.30997859, 0.30000000 0.31000000, 0.30000000 0.300000
00))

SQLite

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

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

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

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

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

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

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

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

INSERT INTO waste_sites (site) VALUES (
 st_geometry ('point (.30 .30)', 4326)
);

--Replace hs.id with ID value of second record in waste_sites table if not 2.
SELECT sa.id, st_astext (st_intersection (st_buffer (hs.site, .01), sa.shape))
 AS "Intersection"
 FROM population sa, waste_sites hs
 WHERE hs.id = 2
 AND st_astext (st_intersection (st_buffer (hs.site, .1), sa.shape)) 
 NOT LIKE '%EMPTY%';

  id  Intersection

1     POLYGON (( 0.29000000 0.30000000, 0.30000000 0.30000000, 0.30000000
0.31000000, 0.29934597 0.30997859, 0.29869474 0.30991445, 0.29804910 0.30980785,
 0.29741181 0.30965926, 0.29678561 0.30946930, 0.29617317 0.30923880, 0.29557711
 0.30896873, 0.29500000 0.30866025, 0.29444430 0.30831470, 0.29391239 0.30793353
, 0.29340654 0.30751840, 0.29292893 0.30707107, 0.29248160 0.30659346, 0.2920664
7 0.30608761, 0.29168530 0.30555570, 0.29133975 0.30500000, 0.29103127 0.3044228
9, 0.29076121 0.30382683, 0.29053070 0.30321440, 0.29034074 0.30258819, 0.290192
15 0.30195090, 0.29008555 0.30130526, 0.29002141 0.30065403, 0.29000000 0.300000
00))

2     POLYGON (( 0.30000000 0.30000000, 0.31000000 0.30000000, 0.30997859
0.30065403, 0.30991445 0.30130526, 0.30980785 0.30195090, 0.30965926 0.30258819,
 0.30946930 0.30321440, 0.30923880 0.30382683, 0.30896873 0.30442289, 0.30866025
 0.30500000, 0.30831470 0.30555570, 0.30793353 0.30608761, 0.30751840 0.30659346
, 0.30707107 0.30707107, 0.30659346 0.30751840, 0.30608761 0.30793353, 0.3055557
0 0.30831470, 0.30500000 0.30866025, 0.30442289 0.30896873, 0.30382683 0.3092388
0, 0.30321440 0.30946930, 0.30258819 0.30965926, 0.30195090 0.30980785, 0.301305
26 0.30991445, 0.30065403 0.30997859, 0.30000000 0.31000000, 0.30000000 0.300000
00))