Area({poly|mpoly})

ST_Area() and Area() are synonyms. For more information, see the description of ST_Area().

Centroid({poly|mpoly})

ST_Centroid() and Centroid() are synonyms. For more information, see the description of ST_Centroid().

ExteriorRing(poly)

ST_ExteriorRing() and ExteriorRing() are synonyms. For more information, see the description of ST_ExteriorRing().

InteriorRingN(poly, N)

ST_InteriorRingN() and InteriorRingN() are synonyms. For more information, see the description of ST_InteriorRingN().

NumInteriorRings(poly)

ST_NumInteriorRings() and NumInteriorRings() are synonyms. For more information, see the description of ST_NumInteriorRings().

ST_Area({poly|mpoly})

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 |
+----------------------------------+

ST_Area() and Area() are synonyms.

ST_Centroid({poly|mpoly})

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.

ST_ExteriorRing(poly)

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.

ST_InteriorRingN(poly, N)

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.

ST_NumInteriorRings(poly)

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.