ST_Boundary

定义

ST_Boundary 获取一个几何对象，然后以几何对象形式返回其组合边界。

语法

sde.st_boundary (g1 sde.st_geometry)

返回类型

ST_Geometry

示例

在本示例中，创建包含两列的 boundaries 表：定义为 varchar 的 geotype 和定义为超类 ST_Geometry 的 geometry。后续的 INSERT 语句将为每个子类几何添加一条记录。ST_Boundary 函数检索存储在 geometry 列中的每个子类的边界。请注意，生成几何的维度始终小于输入几何的维度。点和多点始终生成表示空几何的边界，维度为 –1。线串和多线串返回多点边界，维度为 0。面或多面始终返回多线串边界，维度为 1。

Oracle

CREATE TABLE boundaries (geotype varchar(20), geometry sde.st_geometry);

INSERT INTO BOUNDARIES VALUES (
'Point',
sde.st_pointfromtext ('point (10.02 20.01)', 0)
);

INSERT INTO BOUNDARIES VALUES (
'Linestring',
sde.st_linefromtext ('linestring (10.02 20.01, 10.32 23.98, 11.92 25.64)', 0)
);

INSERT INTO BOUNDARIES VALUES (
'Polygon',
sde.st_polyfromtext ('polygon ((10.02 20.01, 11.92 35.64, 25.02 34.15, 19.15 33.94, 10.02 20.01))', 0)
);

INSERT INTO BOUNDARIES VALUES (
'Multipoint',
sde.st_mpointfromtext ('multipoint (10.02 20.01, 10.32 23.98, 11.92 25.64)', 0)
);

INSERT INTO BOUNDARIES VALUES (
'Multilinestring',
sde.st_mlinefromtext ('multilinestring ((10.02 20.01, 10.32 23.98, 11.92 25.64), (9.55 23.75, 15.36 30.11))', 0)
);

INSERT INTO BOUNDARIES VALUES (
'Multipolygon',
sde.st_mpolyfromtext ('multipolygon (((10.02 20.01, 11.92 35.64, 25.02 34.15, 19.15 33.94, 10.02 20.01), (51.71 21.73,73.36 27.04,71.52 32.87, 52.43 31.90, 51.71 21.73)))', 0)
);

SELECT type, sde.st_astext (sde.st_boundary (geometry)) "The boundary"
FROM BOUNDARIES;

GEOTYPE            The boundary

Point              POINT EMPTY
Linestring         MULTIPOINT(10.02000000 20.01000000, 11.92000000 25.64000000)
Polygon            MULTILINESTRING ((10.02000000 20.01000000, 19.15000000 33.94000000,25.02000000 34.15000000, 11.92000000 35.64000000, 10.02000000 20.01000000))
Multipoint         POINT EMPTY
Multilinestring    MULTIPOINT (9.55000000 23.75000000, 10.02000000 20.01000000, 11.92000000 25.64000000, 15.36000000 30.11000000)
Multipolygon       MULTILINESTRING((51.71000000 21.73000000, 73.36000000 27.04000000, 71.52000000 32.87000000, 52.43000000 31.90000000, 51.71000000 21.73000000), (10.02000000 20.01000000, 19.15000000 33.94000000, 25.02000000 34.15000000, 11.92000000 35.64000000, 10.02000000 20.01000000))

PostgreSQL

CREATE TABLE boundaries (type varchar(20), geometry st_geometry);

INSERT INTO boundaries VALUES (
'Point',
st_point ('point (10.02 20.01)', 0)
);

INSERT INTO boundaries VALUES (
'Linestring',
st_linestring ('linestring (10.02 20.01, 10.32 23.98, 11.92 25.64)', 0)
);

INSERT INTO boundaries VALUES (
'Polygon',
st_polygon ('polygon ((10.02 20.01, 11.92 35.64, 25.02 34.15, 19.15 33.94, 10.02 20.01))', 0)
);

INSERT INTO boundaries VALUES (
'Multipoint',
st_multipoint ('multipoint (10.02 20.01, 10.32 23.98, 11.92 25.64)', 0)
);

INSERT INTO boundaries VALUES (
'Multilinestring',
st_multilinestring ('multilinestring ((10.02 20.01, 10.32 23.98, 11.92 25.64), 
(9.55 23.75, 15.36 30.11))', 0)
);

INSERT INTO boundaries VALUES (
'Multipolygon',
st_multipolygon ('multipolygon (((10.02 20.01, 11.92 35.64, 25.02 34.15, 19.15 33.94, 10.02 20.01), 
(51.71 21.73, 73.36 27.04, 71.52 32.87, 52.43 31.90, 51.71 21.73)))', 0)
);

SELECT type, st_astext (st_boundary (geometry)) 
AS "The boundary"
FROM boundaries;

type              The boundary

Point              EMPTY
Linestring         MULTIPOINT(10.02000000 20.01000000, 11.92000000 
25.64000000)
Polygon            LINESTRING ((10.02000000 20.01000000, 19.15000000 
33.94000000,25.02000000 34.15000000, 11.92000000 35.64000000, 10.02000000
20.01000000))
Multipoint         EMPTY
Multilinestring    MULTIPOINT (9.55000000 23.75000000, 10.02000000 
20.01000000, 11.92000000 25.64000000, 15.36000000 30.11000000)
Multipolygon       MULTILINESTRING((51.71000000 21.73000000, 73.36000000
27.04000000, 71.52000000 32.87000000, 52.43000000 31.90000000,
51.71000000 21.73000000), (10.02000000 20.01000000, 19.15000000
33.94000000, 25.02000000 34.15000000, 11.92000000 35.64000000, 
10.02000000 20.01000000))