當輸入Geometry對象在判定條件ST_IsClosed下為true且ST_IsSimple也為true時，返回true。
文法
boolean ST_IsRing(geometry g);參數
| 參數名稱 | 描述 |
| g | 目標Geometry對象。 |
樣本
- 返回true的情況：
SELECT ST_IsRing(geom), ST_IsClosed(geom), ST_IsSimple(geom) FROM (SELECT 'LINESTRING(0 0,0 2,2 0,0 0)'::geometry AS geom) AS test; st_isring | st_isclosed | st_issimple -----------+-------------+------------- t | t | t (1 row) - 返回false的情況：
SELECT ST_IsRing(geom), ST_IsClosed(geom), ST_IsSimple(geom) FROM (SELECT 'LINESTRING(0 0,0 2,0 0)'::geometry AS geom) AS test; st_isring | st_isclosed | st_issimple -----------+-------------+------------- f | t | f (1 row)