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ST_Equals

定义

ST_Equals 比较两个几何，如果这两个几何完全相同，则返回 1（Oracle 和 SQLite）或 t (PostgreSQL)；否则返回 0（Oracle 和 SQLite）或 f (PostgreSQL)。

语法

Oracle 和 PostgreSQL

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

SQLite

st_equals (geometry1 geometryblob, geometry2 geometryblob)

返回类型

布尔型

示例

城市 GIS 技术人员怀疑 studies 表中的某些数据存在重复。为减轻顾虑，他查询该表，以确定是否存在相等的形状多面。

通过以下语句创建并填充 studies 表。id 列唯一标识研究区域，而形状字段存储区域的几何。

接下来，通过 equal 谓词将 studies 表与其本身进行空间连接，只要发现两个多面相等，就会返回 1（Oracle 和 SQLite）或 t (PostgreSQL)。s1.id<>s2.id 条件不用将几何与其本身进行比较。

Oracle

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

INSERT INTO studies (id, shape) VALUES (
 1,
 sde.st_polygon ('polygon ((0 0, 0 10, 10 10, 10 0, 0 0))', 4326)
);

INSERT INTO studies (id, shape) VALUES (
 2,
 sde.st_polygon ('polygon ((20 0, 20 10, 30 10, 30 0, 20 0))', 4326)
);

INSERT INTO studies (id, shape) VALUES (
 3,
 sde.st_polygon ('polygon ((40 0, 40 10, 50 10, 50 0, 40 0))', 4326)
);

INSERT INTO studies (id, shape) VALUES (
 4,
 sde.st_polygon ('polygon ((0 0, 0 10, 10 10, 10 0, 0 0))', 4326)
);

SELECT UNIQUE (s1.id), s2.id
 FROM STUDIES s1, STUDIES s2
 WHERE sde.st_equals (s1.shape, s2.shape) = 1
 AND s1.id <> s2.id;

ID     ID

 4       1
 1       4

PostgreSQL

CREATE TABLE studies (
 id serial,
 shape st_geometry
);

INSERT INTO studies (shape) VALUES (
 st_polygon ('polygon ((0 0, 0 10, 10 10, 10 0, 0 0))', 4326)
);

INSERT INTO studies (shape) VALUES (
 st_polygon ('polygon ((20 0, 20 10, 30 10, 30 0, 20 0))', 4326)
);

INSERT INTO studies (shape) VALUES (
 st_polygon ('polygon ((40 0, 40 10, 50 10, 50 0, 40 0))', 4326)
);

INSERT INTO studies (shape) VALUES (
 st_polygon ('polygon ((0 0, 0 10, 10 10, 10 0, 0 0))', 4326)
);

SELECT DISTINCT (s1.id), s2.id
 FROM studies s1, studies s2 
 WHERE st_equals (s1.shape, s2.shape) = 't'
 AND s1.id <> s2.id;

id    id

 1      4
 4      1

SQLite

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

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

INSERT INTO studies (shape) VALUES (
 st_polygon ('polygon ((0 0, 0 10, 10 10, 10 0, 0 0))', 4326)
);

INSERT INTO studies (shape) VALUES (
 st_polygon ('polygon ((20 0, 20 10, 30 10, 30 0, 20 0))', 4326)
);

INSERT INTO studies (shape) VALUES (
 st_polygon ('polygon ((40 0, 40 10, 50 10, 50 0, 40 0))', 4326)
);

INSERT INTO studies (shape) VALUES (
 st_polygon ('polygon ((0 0, 0 10, 10 10, 10 0, 0 0))', 4326)
);

SELECT DISTINCT (s1.id), s2.id
 FROM studies s1, studies s2 
 WHERE st_equals (s1.shape, s2.shape) = 1
 AND s1.id <> s2.id;

id    id

 1      4
 4      1

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