ST_NumInteriorRings(poly) NumInteriorRings(poly)
Returns an integer containing the number of interior rings in the Polygon value poly
.
Note that according the 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
.
ST_NumInteriorRings()
and NumInteriorRings()
are synonyms.
SET @poly = 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))'; SELECT NumInteriorRings(GeomFromText(@poly)); +---------------------------------------+ | NumInteriorRings(GeomFromText(@poly)) | +---------------------------------------+ | 1 | +---------------------------------------+
Non-overlapping 'polygon':
SELECT ST_NumInteriorRings(ST_PolyFromText('POLYGON((0 0,10 0,10 10,0 10,0 0), (-1 -1,-5 -1,-5 -5,-1 -5,-1 -1))')) AS NumInteriorRings; +------------------+ | NumInteriorRings | +------------------+ | 1 | +------------------+
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Licensed under the Creative Commons Attribution 3.0 Unported License and the GNU Free Documentation License.
https://mariadb.com/kb/en/numinteriorrings/