ST_NumInteriorRings — 返回多边形的内环(孔)数。
integer ST_NumInteriorRings(
geometry a_polygon)
;
返回多边形几何体的内环数量。如果几何体不是多边形,则返回NULL。
This method implements the SQL/MM specification. SQL-MM 3:8.2.5
已更改:2.0.0-在以前的版本中,它允许传递MULTIPOLYGON,返回第一个多边形的内部环数。
--If you have a regular polygon SELECT gid, field1, field2, ST_NumInteriorRings(geom) AS numholes FROM sometable; --If you have multipolygons --And you want to know the total number of interior rings in the MULTIPOLYGON SELECT gid, field1, field2, SUM(ST_NumInteriorRings(geom)) AS numholes FROM (SELECT gid, field1, field2, (ST_Dump(geom)).geom As geom FROM sometable) As foo GROUP BY gid, field1,field2;