名称
ST_IsRing — 检测线串是闭合的还是简单的。
大纲
boolean ST_IsRing(geometry g);
描述
Returns TRUE if this LINESTRING is both ST_IsClosed (ST_StartPoint(g) ~= ST_EndPoint(g)) and ST_IsSimple (does not self intersect).
此方法实现了 SQL 1.1 的 OGC 简单功能规范。 2.1.5.1
该方法实现了SQL/MM规范。 SQL-MM 3: 7.1.6
![[注意]](../images/note.png)
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SQL-MM 定义了 |
示例
Code
SELECT ST_IsRing(geom), ST_IsClosed(geom), ST_IsSimple(geom) FROM (SELECT 'LINESTRING(0 0,0 1,1 1,1 0,0 0)'::geometry AS geom) AS foo;
栅格输出
st_isring | st_isclosed | st_issimple -----------+-------------+------------- t | t | t (1 row)
Figure
Code
SELECT ST_IsRing(geom), ST_IsClosed(geom), ST_IsSimple(geom) FROM (SELECT 'LINESTRING(0 0,0 1,1 0,1 1,0 0)'::geometry AS geom) AS foo;
栅格输出
st_isring | st_isclosed | st_issimple -----------+-------------+------------- f | t | f (1 row)
Figure