Constructs a Polygon value from a list of WKB LineString arguments. It defines a filled shape using an outer ring and optional inner rings (holes).
Polygon(ls1,ls2,...)Constructs a WKB Polygon value from a number of WKB LineString
arguments. If any argument does not represent the WKB of a LinearRing (that is,
not a closed and simple LineString) the return value is NULL.
Note that according to 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 will return 1.
Non-overlapping 'polygon':
Polygon_Example:
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SET @g = ST_GEOMFROMTEXT('POLYGON((1 1,1 5,4 9,6 9,9 3,7 2,1 1))');
CREATE TABLE gis_polygon (g POLYGON);
INSERT INTO gis_polygon VALUES
(PolygonFromText('POLYGON((10 10,20 10,20 20,10 20,10 10))')),
(PolyFromText('POLYGON((0 0,50 0,50 50,0 50,0 0), (10 10,20 10,20 20,10 20,10 10))')),
(PolyFromWKB(AsWKB(Polygon(LineString(Point(0, 0), Point(30, 0), Point(30, 30), Point(0, 0))))));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 |
+------------------+CREATE TABLE polygon_example (
p POLYGON
);INSERT INTO polygon_example VALUES
(ST_PolygonFromText('POLYGON((0 40, 0 20, 6 30, 12 20, 12 40, 0 40))')),
(ST_PolyFromText('POLYGON((15 40, 15 20, 25 20, 30 25, 30 35, 25 40, 15 40))')),
(Polygon(LineString(Point(0, 0), Point(0, 1), Point(1, 1),
Point(1, 0), Point(0, 0))));SELECT ST_AsWKT(p) FROM polygon_example;+------------------------------------------------------+
| ST_AsWKT(p) |
+------------------------------------------------------+
| POLYGON((0 40,0 20,6 30,12 20,12 40,0 40)) |
| POLYGON((15 40,15 20,25 20,30 25,30 35,25 40,15 40)) |
| POLYGON((0 0,0 1,1 1,1 0,0 0)) |
+------------------------------------------------------+