MySQL 5.6 Reference Manual Including MySQL NDB Cluster 7.3-7.4 Reference Guide
Functions in this section return properties of
Polygon
or MultiPolygon
values.
ST_Area()
and
Area()
are synonyms. For more
information, see the description of
ST_Area()
.
ST_Centroid()
and
Centroid()
are synonyms. For
more information, see the description of
ST_Centroid()
.
ST_ExteriorRing()
and
ExteriorRing()
are synonyms.
For more information, see the description of
ST_ExteriorRing()
.
ST_InteriorRingN()
and
InteriorRingN()
are synonyms.
For more information, see the description of
ST_InteriorRingN()
.
ST_NumInteriorRings()
and
NumInteriorRings()
are
synonyms. For more information, see the description of
ST_NumInteriorRings()
.
Returns a double-precision number indicating the area of the
Polygon
or
MultiPolygon
argument, as measured in its
spatial reference system. For arguments of dimension 0 or 1,
the result is 0. If the argument is an empty geometry the
return value is 0. If the argument is
NULL
the return value is
NULL
.
mysql>SET @poly =
'Polygon((0 0,0 3,3 0,0 0),(1 1,1 2,2 1,1 1))';
mysql>SELECT ST_Area(ST_GeomFromText(@poly));
+---------------------------------+ | ST_Area(ST_GeomFromText(@poly)) | +---------------------------------+ | 4 | +---------------------------------+ 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 ST_Area(ST_GeomFromText(@mpoly));
+----------------------------------+ | ST_Area(ST_GeomFromText(@mpoly)) | +----------------------------------+ | 8 | +----------------------------------+
Returns the mathematical centroid for the
Polygon
or
MultiPolygon
argument as a
Point
. The result is not guaranteed to be
on the MultiPolygon
. If the argument is
NULL
or an empty geometry, the return
value is NULL
.
mysql>SET @poly =
ST_GeomFromText('POLYGON((0 0,10 0,10 10,0 10,0 0),(5 5,7 5,7 7,5 7,5 5))');
mysql>SELECT GeometryType(@poly),ST_AsText(ST_Centroid(@poly));
+---------------------+--------------------------------------------+ | GeometryType(@poly) | ST_AsText(ST_Centroid(@poly)) | +---------------------+--------------------------------------------+ | POLYGON | POINT(4.958333333333333 4.958333333333333) | +---------------------+--------------------------------------------+
ST_Centroid()
and
Centroid()
are synonyms.
Returns the exterior ring of the Polygon
value poly
as a
LineString
. If the argument is
NULL
or an empty geometry, the return
value is NULL
.
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 ST_AsText(ST_ExteriorRing(ST_GeomFromText(@poly)));
+----------------------------------------------------+ | ST_AsText(ST_ExteriorRing(ST_GeomFromText(@poly))) | +----------------------------------------------------+ | LINESTRING(0 0,0 3,3 3,3 0,0 0) | +----------------------------------------------------+
ST_ExteriorRing()
and
ExteriorRing()
are synonyms.
Returns the N
-th interior ring
for the Polygon
value
poly
as a
LineString
. Rings are numbered beginning
with 1. If the argument is NULL
or an
empty geometry, the return value is NULL
.
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 ST_AsText(ST_InteriorRingN(ST_GeomFromText(@poly),1));
+-------------------------------------------------------+ | ST_AsText(ST_InteriorRingN(ST_GeomFromText(@poly),1)) | +-------------------------------------------------------+ | LINESTRING(1 1,1 2,2 2,2 1,1 1) | +-------------------------------------------------------+
ST_InteriorRingN()
and
InteriorRingN()
are synonyms.
Returns the number of interior rings in the
Polygon
value
poly
. If the argument is
NULL
or an empty geometry, the return
value is NULL
.
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 ST_NumInteriorRings(ST_GeomFromText(@poly));
+---------------------------------------------+ | ST_NumInteriorRings(ST_GeomFromText(@poly)) | +---------------------------------------------+ | 1 | +---------------------------------------------+
ST_NumInteriorRings()
and
NumInteriorRings()
are
synonyms.