ST_NRings — 返回多边形几何体中的环形数。
integer ST_NRings(geometry geomA);
integer ST_NRings(
)
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
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)
ST_NumInteriorRings