Functions in this section return properties of
Polygon
or MultiPolygon
values.
Unless otherwise specified, functions in this section handle their geometry arguments as follows:
If any argument is
NULL
or any geometry argument is an empty geometry, the return value isNULL
.If any geometry argument is not a syntactically well-formed geometry, an
ER_GIS_INVALID_DATA
error occurs.If any geometry argument is a syntactically well-formed geometry in an undefined spatial reference system (SRS), an
ER_SRS_NOT_FOUND
error occurs.For functions that take multiple geometry arguments, if those arguments are not in the same SRS, an
ER_GIS_DIFFERENT_SRIDS
error occurs.Otherwise, the return value is non-
NULL
.
These functions are available for obtaining polygon properties:
Returns a double-precision number indicating the area of the
Polygon
orMultiPolygon
argument, as measured in its spatial reference system.As of MySQL 8.0.13,
ST_Area()
handles its arguments as described in the introduction to this section, with these exceptions:If the geometry is geometrically invalid, either the result is an undefined area (that is, it can be any number), or an error occurs.
If the geometry is valid but is not a
Polygon
orMultiPolygon
object, anER_UNEXPECTED_GEOMETRY_TYPE
error occurs.If the geometry is a valid
Polygon
in a Cartesian SRS, the result is the Cartesian area of the polygon.If the geometry is a valid
MultiPolygon
in a Cartesian SRS, the result is the sum of the Cartesian area of the polygons.If the geometry is a valid
Polygon
in a geographic SRS, the result is the geodetic area of the polygon in that SRS, in square meters.If the geometry is a valid
MultiPolygon
in a geographic SRS, the result is the sum of geodetic area of the polygons in that SRS, in square meters.If an area computation results in
+inf
, anER_DATA_OUT_OF_RANGE
error occurs.If the geometry has a geographic SRS with a longitude or latitude that is out of range, an error occurs:
If a longitude value is not in the range (−180, 180], an
ER_GEOMETRY_PARAM_LONGITUDE_OUT_OF_RANGE
error occurs (ER_LONGITUDE_OUT_OF_RANGE
prior to MySQL 8.0.12).If a latitude value is not in the range [−90, 90], an
ER_GEOMETRY_PARAM_LATITUDE_OUT_OF_RANGE
error occurs (ER_LATITUDE_OUT_OF_RANGE
prior to MySQL 8.0.12).
Ranges shown are in degrees. The exact range limits deviate slightly due to floating-point arithmetic.
Prior to MySQL 8.0.13,
ST_Area()
handles its arguments as described in the introduction to this section, with these exceptions:For arguments of dimension 0 or 1, the result is 0.
If a geometry is empty, the return value is 0 rather than
NULL
.For a geometry collection, the result is the sum of the area values of all components. If the geometry collection is empty, its area is returned as 0.
If the geometry has an SRID value for a geographic spatial reference system (SRS), an
ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS
error occurs.
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
orMultiPolygon
argument as aPoint
. The result is not guaranteed to be on theMultiPolygon
.This function processes geometry collections by computing the centroid point for components of highest dimension in the collection. Such components are extracted and made into a single
MultiPolygon
,MultiLineString
, orMultiPoint
for centroid computation.ST_Centroid()
handles its arguments as described in the introduction to this section, with these exceptions:The return value is
NULL
for the additional condition that the argument is an empty geometry collection.If the geometry has an SRID value for a geographic spatial reference system (SRS), an
ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS
error occurs.
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 ST_GeometryType(@poly),ST_AsText(ST_Centroid(@poly)); +------------------------+--------------------------------------------+ | ST_GeometryType(@poly) | ST_AsText(ST_Centroid(@poly)) | +------------------------+--------------------------------------------+ | POLYGON | POINT(4.958333333333333 4.958333333333333) | +------------------------+--------------------------------------------+
Returns the exterior ring of the
Polygon
valuepoly
as aLineString
.ST_ExteriorRing()
handles its arguments as described in the introduction to this section.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) | +----------------------------------------------------+
Returns the
N
-th interior ring for thePolygon
valuepoly
as aLineString
. Rings are numbered beginning with 1.ST_InteriorRingN()
handles its arguments as described in the introduction to this section.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_NumInteriorRing(
,poly
)ST_NumInteriorRings(
poly
)Returns the number of interior rings in the
Polygon
valuepoly
.ST_NumInteriorRing()
andST_NuminteriorRings()
handle their arguments as described in the introduction to this section.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 | +---------------------------------------------+