ST_IsClosed

定义

ST_IsClosed 以 ST_LineString 或 ST_MultiLineString 作为输入参数，如果为闭合，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_isclosed (line1 sde.st_geometry)
sde.st_isclosed (multiline1 sde.st_geometry)

SQLite

st_isclosed (geometry1 geometryblob)

返回类型

布尔型

示例

测试线串

创建一个包含单一 linestring 列的 closed_linestring 表。

INSERT 语句将两条记录插入 closed_linestring 表中。第一条记录不是闭合线串，而第二条记录是闭合线串。

查询将返回 ST_IsClosed 函数的结果。因为第一行的线串不闭合，所以返回 0 或 f；而第二行的线串是闭合的，所以返回 1 或 t。

Oracle

CREATE TABLE closed_linestring (ln1 sde.st_geometry);

INSERT INTO CLOSED_LINESTRING VALUES (
 sde.st_linefromtext ('linestring (10.02 20.01, 10.32 23.98, 11.92 25.64)', 4326)
);

INSERT INTO CLOSED_LINESTRING VALUES (
 sde.st_linefromtext ('linestring (10.02 20.01, 11.92 35.64, 25.02 34.15, 19.15 33.94, 10.02 20.01)', 4326)
);

SELECT sde.st_isclosed (ln1) Is_it_closed
 FROM CLOSED_LINESTRING;

Is_it_closed

0
1

PostgreSQL

CREATE TABLE closed_linestring (ln1 sde.st_geometry);

INSERT INTO closed_linestring VALUES (
 sde.st_linestring ('linestring (10.02 20.01, 10.32 23.98, 11.92 25.64)', 4326)
);

INSERT INTO closed_linestring VALUES (
sde.st_linestring ('linestring (10.02 20.01, 11.92 35.64, 25.02 34.15, 19.15 33.94, 10.02 20.01)', 4326)
);

SELECT sde.st_isclosed (ln1) AS Is_it_closed
FROM closed_linestring;

is_it_closed

f
t

SQLite

CREATE TABLE closed_linestring (id integer);

SELECT AddGeometryColumn (
 NULL,
 'closed_linestring',
 'ln1',
 4326,
 'linestring',
 'xy',
 'null'
);

INSERT INTO closed_linestring VALUES (
 1,
 st_linefromtext ('linestring (10.02 20.01, 10.32 23.98, 11.92 25.64)', 4326)
);

INSERT INTO closed_linestring VALUES (
 2,
 st_linefromtext ('linestring (10.02 20.01, 11.92 35.64, 25.02 34.15, 19.15 33.94, 10.02 20.01)', 4326)
);

SELECT st_isclosed (ln1)
 AS "Is_it_closed"
 FROM closed_linestring;

Is_it_closed

0
1

测试多线串

创建一个包含单一 ST_MultiLineString 列的 closed_mlinestring 表。

INSERT 语句将分别插入一条闭合的和一条不闭合的 ST_MultiLineString 记录。

查询将列出 ST_IsClosed 函数的结果。因为第一行的多线串不闭合，所以返回 0 或 f。而第二行 ln1 列中存储的多线串是闭合的，所以返回 1 或 t。如果多线串的所有线串元素都闭合，则多线串是闭合的。

Oracle

CREATE TABLE closed_mlinestring (mln1 sde.st_geometry);

INSERT INTO closed_mlinestring VALUES (
 sde.st_mlinefromtext ('multilinestring ((10.02 20.01, 10.32 23.98, 11.92 25.64), (9.55 23.75, 15.36 30.11))', 4326)
);

INSERT INTO closed_mlinestring VALUES (
 sde.st_mlinefromtext ('multilinestring ((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))', 4326)
);

SELECT sde.st_isclosed (mln1) Is_it_closed
 FROM CLOSED_MLINESTRING;

Is_it_closed

0
1

PostgreSQL

CREATE TABLE closed_mlinestring (mln1 sde.st_geometry);

INSERT INTO closed_mlinestring VALUES (
 sde.st_mlinefromtext ('multilinestring ((10.02 20.01, 10.32 23.98, 11.92 25.64), (9.55 23.75, 15.36 30.11))', 4326)
);

INSERT INTO closed_mlinestring VALUES (
 sde.st_mlinefromtext ('multilinestring ((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))', 4326)
);

SELECT st_isclosed (mln1)
 AS Is_it_closed
 FROM closed_mlinestring;

is_it_closed

f
t

SQLite

CREATE TABLE closed_mlinestring (mln1 geometryblob);

SELECT AddGeometryColumn (
 NULL,
 'closed_mlinestring',
 'mln1',
 4326,
 'multilinestring',
 'xy',
 'null'
);

INSERT INTO closed_mlinestring VALUES (
 st_mlinefromtext ('multilinestring ((10.02 20.01, 10.32 23.98, 11.92 25.64), (9.55 23.75, 15.36 30.11))', 4326)
);

INSERT INTO closed_mlinestring VALUES (
 st_mlinefromtext ('multilinestring ((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))', 4326)
);

SELECT sde.st_isclosed (mln1)
 AS "Is_it_closed"
 FROM CLOSED_MLINESTRING;

Is_it_closed

0
1