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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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