Oracle 5.0, Справочное руководство

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Spatial Analysis Functions
994
+---------------------------+
| Area(GeomFromText(@poly)) |
+---------------------------+
| 4 |
+---------------------------+
•
ExteriorRing(poly)
[994]
Returns the exterior ring of the
Polygon
value
poly
as a
LineString
.
mysql> SET @poly =
-> 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';
mysql> SELECT AsText(ExteriorRing(GeomFromText(@poly)));
+-------------------------------------------+
| AsText(ExteriorRing(GeomFromText(@poly))) |
+-------------------------------------------+
| LINESTRING(0 0,0 3,3 3,3 0,0 0) |
+-------------------------------------------+
•
InteriorRingN(poly,N)
[994]
Returns the
N
-th interior ring for the
Polygon
value
poly
as a
LineString
. Rings are numbered
beginning with 1.
mysql> SET @poly =
-> 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';
mysql> SELECT AsText(InteriorRingN(GeomFromText(@poly),1));
+----------------------------------------------+
| AsText(InteriorRingN(GeomFromText(@poly),1)) |
+----------------------------------------------+
| LINESTRING(1 1,1 2,2 2,2 1,1 1) |
+----------------------------------------------+
•
NumInteriorRings(poly)
[994]
Returns the number of interior rings in the
Polygon
value
poly
.
mysql> SET @poly =
-> 'Polygon((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1))';
mysql> SELECT NumInteriorRings(GeomFromText(@poly));
+---------------------------------------+
| NumInteriorRings(GeomFromText(@poly)) |
+---------------------------------------+
| 1 |
+---------------------------------------+
12.16.5.2.6.
MultiPolygon
Functions
These functions return properties of
MultiPolygon
values.
•
Area(mpoly)
[993]
Returns as a double-precision number the area of the
MultiPolygon
value
mpoly
, as measured in
its spatial reference system.
mysql> SET @mpoly =
-> 'MultiPolygon(((0 0,0 3,3 3,3 0,0 0),(1 1,1 2,2 2,2 1,1 1)))';
mysql> SELECT Area(GeomFromText(@mpoly));
+----------------------------+
| Area(GeomFromText(@mpoly)) |
+----------------------------+
| 8 |
+----------------------------+
•
Centroid(mpoly)
[994]
Returns the mathematical centroid for the
MultiPolygon
value
mpoly
as a
Point
. The result is
not guaranteed to be on the
MultiPolygon
.