MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6
A Polygon is a planar
Surface representing a multisided geometry.
It is defined by a single exterior boundary and zero or more
interior boundaries, where each interior boundary defines a
hole in the Polygon.
Polygon
Examples
On a region map, Polygon objects could
represent forests, districts, and so on.
Polygon
Assertions
The boundary of a Polygon consists of a
set of LinearRing objects (that is,
LineString objects that are both simple
and closed) that make up its exterior and interior
boundaries.
A Polygon has no rings that cross. The
rings in the boundary of a Polygon may
intersect at a Point, but only as a
tangent.
A Polygon has no lines, spikes, or
punctures.
A Polygon has an interior that is a
connected point set.
A Polygon may have holes. The exterior
of a Polygon with holes is not
connected. Each hole defines a connected component of the
exterior.
The preceding assertions make a Polygon a
simple geometry.