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The functions listed in this ssection do not restrict their argument and accept a geometry value of any type.
GeometryType(g)
g
is a member.
The name will correspond to one of the instantiable Geometry
subclasses.
mysql> SELECT GeometryType(GeomFromText('POINT(1 1)')); +------------------------------------------+ | GeometryType(GeomFromText('POINT(1 1)')) | +------------------------------------------+ | POINT | +------------------------------------------+ |
Dimension(g)
g
. The result
can be -1, 0, 1, or 2. (The meaning of these values is given in
17.2.2 Class Geometry
.)
mysql> SELECT Dimension(GeomFromText('LineString(1 1,2 2)')); +------------------------------------------------+ | Dimension(GeomFromText('LineString(1 1,2 2)')) | +------------------------------------------------+ | 1 | +------------------------------------------------+ |
SRID(g)
g
.
mysql> SELECT SRID(GeomFromText('LineString(1 1,2 2)',101)); +-----------------------------------------------+ | SRID(GeomFromText('LineString(1 1,2 2)',101)) | +-----------------------------------------------+ | 101 | +-----------------------------------------------+ |
Envelope(g)
g
.
The result is returned as a polygon value.
mysql> SELECT AsText(Envelope(GeomFromText('LineString(1 1,2 2)'))); +-------------------------------------------------------+ | AsText(Envelope(GeomFromText('LineString(1 1,2 2)'))) | +-------------------------------------------------------+ | POLYGON((1 1,2 1,2 2,1 2,1 1)) | +-------------------------------------------------------+ |
The polygon is defined by the corner points of the bounding box:
POLYGON((MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY)) |
The OpenGIS specification also defines the following functions, which MySQL does not implement:
Boundary(g)
g
.
IsEmpty(g)
g
is the empty geometry, 0 if it is not
empty, and -1 if the argument is NULL
.
If the geometry is empty, it represents the empty point set.
IsSimple(g)
Currently, this function is a placeholder and should not be used. If implemented, its behavior will be as described in the next paragraph.
Returns 1 if the geometry value g
has no anomalous geometric points,
such as self intersection or self tangency. IsSimple()
returns 0 if the
argument is not simple, and -1 if it is NULL
.
The description of each instantiable geometric class given earlier in the chapter includes the specific conditions that cause an instance of that class to be classified as not simple.
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