Syntax\n------\n\nST_NumInteriorRings(poly)\nNumInteriorRings(poly)\n\nDescription\n-----------\n\nReturns an integer containing the number of interior rings in the Polygon value poly.\n\nNote that according the OpenGIS standard, a POLYGON should have exactly one ExteriorRing and all other rings should lie within that ExteriorRing and thus be the InteriorRings. Practically, however, some systems, including MariaDB's, permit polygons to have several 'ExteriorRings'. In the case of there being multiple, non-overlapping exterior rings ST_NumInteriorRings() will return 1.\n\nST_NumInteriorRings() and NumInteriorRings() are synonyms.\n\nExamples\n--------\n\nSET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';\n\nSELECT NumInteriorRings(GeomFromText(@poly));\n+---------------------------------------+\n| NumInteriorRings(GeomFromText(@poly)) |\n+---------------------------------------+\n|                                     1 |\n+---------------------------------------+\n\nURL: https://mariadb.com/docs/server/reference/sql-statements/geometry-constructors/polygon-properties/st_numinteriorrings