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MySQL 5.5 Reference Manual  /  ...  /  General Geometry Property Functions General Geometry Property Functions

The functions listed in this section do not restrict their argument and accept a geometry value of any type.

  • Dimension(g)

    Returns the inherent dimension of the geometry value g. The result can be −1, 0, 1, or 2. The meaning of these values is given in Section, “Geometry Class”.

    mysql> SELECT Dimension(GeomFromText('LineString(1 1,2 2)'));
    | Dimension(GeomFromText('LineString(1 1,2 2)')) |
    |                                              1 |
  • Envelope(g)

    Returns the minimum bounding rectangle (MBR) for the geometry value g. The result is returned as a Polygon value that is defined by the corner points of the bounding box:

    mysql> SELECT AsText(Envelope(GeomFromText('LineString(1 1,2 2)')));
    | AsText(Envelope(GeomFromText('LineString(1 1,2 2)'))) |
    | POLYGON((1 1,2 1,2 2,1 2,1 1))                        |
  • GeometryType(g)

    Returns a binary string indicating the name of the geometry type of which the geometry instance g is a member. The name corresponds to one of the instantiable Geometry subclasses.

    mysql> SELECT GeometryType(GeomFromText('POINT(1 1)'));
    | GeometryType(GeomFromText('POINT(1 1)')) |
    | POINT                                    |
  • IsEmpty(g)

    This function is a placeholder that returns 0 for any valid geometry value, 1 for any invalid geometry value or NULL.

    MySQL does not support GIS EMPTY values such as POINT EMPTY.

  • IsSimple(g)

    In MySQL 5.5, this function is a placeholder that always returns 0.

    The description of each instantiable geometric class given earlier in the chapter includes the specific conditions that cause an instance of that class to be classified as not simple. (See Section, “The Geometry Class Hierarchy”.)

  • SRID(g)

    Returns an integer indicating the Spatial Reference System ID for the geometry value g.

    In MySQL, the SRID value is just an integer associated with the geometry value. All calculations are done assuming Euclidean (planar) geometry.

    mysql> SELECT SRID(GeomFromText('LineString(1 1,2 2)',101));
    | SRID(GeomFromText('LineString(1 1,2 2)',101)) |
    |                                           101 |

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