描述

如果几何体是一个多边形或多个多边形，则返回环形数。与NumInteriorRings不同，它也计算外环。

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

示例

SELECT ST_NRings(geom) As Nrings, ST_NumInteriorRings(geom) As ninterrings
                                        FROM (SELECT ST_GeomFromText('POLYGON((1 2, 3 4, 5 6, 1 2))') As geom) As foo;
         nrings | ninterrings
--------+-------------
          1 |           0
(1 row)

另请参阅

ST_NumInteriorRings