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MySQL 5.6 Reference Manual  /  ...  /  Polygon and MultiPolygon Property Functions

12.16.7.4 Polygon and MultiPolygon Property Functions

Functions in this section return properties of Polygon or MultiPolygon values.

  • 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.


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