定义
ST_Buffer 获取几何对象和距离,然后返回表示围绕源对象的缓冲区的几何对象。
语法
Oracle
sde.st_buffer (geometry sde.st_geometry, distance double_precision) sde.st_buffer (geometry sde.st_geometry, distance double, varchar2 unit_name)
PostgreSQL
sde.st_buffer (geometry sde.st_geometry, distance double_precision) sde.st_buffer (geometry sde.st_geometry, distance double, text unit_name)
SQLite
st_buffer (geometry geometryblob, distance double_precision) st_buffer (geometry geometryblob, distance double, text unit_name)
Unit_name 是缓冲距离的测量单位(例如:米、千米、英尺或英里)。请参阅 Projected coordinate system tables.pdf 中的第一个表,此文件可在 ArcMap 帮助的什么是投影坐标系中访问。
返回类型
Oracle 和 PostgreSQL
ST_Geometry
SQLite
Geometryblob
示例
本示例创建两个表 sensitive_areas 和 hazardous_sites;填充这两个表;使用 ST_Buffer 生成围绕 hazardous_sites 表中的面的缓冲区;然后找出这些缓冲区与 sensitive_areas 面重叠的区域。
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))', 4326)
);
INSERT INTO SENSITIVE_AREAS VALUES (
2,
sde.st_polygon ('polygon ((30 30, 30 50, 50 50, 50 30, 30 30))', 4326)
);
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)', 4326)
);
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 serial,
zone sde.st_geometry
);
CREATE TABLE hazardous_sites (
site_id serial,
name varchar(40),
location sde.st_geometry
);
INSERT INTO sensitive_areas (zone) VALUES (
sde.st_polygon ('polygon ((20 30, 30 30, 30 40, 20 40, 20 30))', 4326)
);
INSERT INTO sensitive_areas (zone) VALUES (
sde.st_polygon ('polygon ((30 30, 30 50, 50 50, 50 30, 30 30))', 4326)
);
INSERT INTO sensitive_areas (zone) VALUES (
sde.st_polygon ('polygon ((40 40, 40 60, 60 60, 60 40, 40 40))', 4326)
);
INSERT INTO hazardous_sites (name, location) VALUES (
'W. H. KleenareChemical Repository',
sde.st_point ('point (60 60)', 4326)
);
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
SQLite
CREATE TABLE sensitive_areas (
id integer primary key autoincrement not null
);
SELECT AddGeometryColumn (
NULL,
'sensitive_areas',
'zone',
4326,
'polygon',
'xy',
'null'
);
CREATE TABLE hazardous_sites (
site_id integer primary key autoincrement not null,
name varchar(40)
);
SELECT AddGeometryColumn (
NULL,
'hazardous_sites',
'location',
4326,
'point',
'xy',
'null'
);
INSERT INTO sensitive_areas (zone) VALUES (
st_polygon ('polygon ((20 30, 30 30, 30 40, 20 40, 20 30))', 4326)
);
INSERT INTO sensitive_areas (zone) VALUES (
st_polygon ('polygon ((30 30, 30 50, 50 50, 50 30, 30 30))', 4326)
);
INSERT INTO sensitive_areas (zone) VALUES (
st_polygon ('polygon ((40 40, 40 60, 60 60, 60 40, 40 40))', 4326)
);
INSERT INTO hazardous_sites (name, location) VALUES (
'W. H. KleenareChemical Repository',
st_point ('point (60 60)', 4326)
);
SELECT sa.id AS "Sensitive Areas", hs.name AS "Hazardous Sites"
FROM sensitive_areas sa, hazardous_sites hs
WHERE st_overlaps (sa.zone, st_buffer (hs.location, .01)) = 1;
Sensitive Areas Hazardous Sites
3 W.H. KleenareChemical Repository