Spatial Extensions in MySQL
***************************

MySQL 4.1 introduces spatial extensions to allow the generation,
storage, and analysis of geographic features.  Currently, these
features are available for MyISAM tables only.

This chapter covers the following topics:

   * The basis of these spatial extensions in the OpenGIS geometry model

   * Data formats for representing spatial data

   * How to use spatial data in MySQL

   * Use of indexing for spatial data

   * MySQL differences from the OpenGIS specification


Introduction
============

 in
the development of publicly available conceptual solutions that can be
useful with all kinds of applications that manage spatial data.  The
OGC maintains a web site at `http://www.opengis.org/'.


This specification is available from the Open GIS web site at
.  It contains
additional information relevant to this chapter.

MySQL implements a subset of the *SQL with Geometry Types* environment
proposed by OGC.  This term refers to an SQL environment that has been
extended with a set of geometry types. A geometry-valued SQL column is
implemented as a column that has a geometry type. The specifications
describe a set of SQL geometry types, as well as functions on those
types to create and analyse geometry values.

A *geographic feature* is anything in the world that has a location.  A
feature can be:

   * An entity. For example, a mountain, a pond, a city.

   * A space. For example, a postcode area, the tropics.

   * A definable location. For example, a crossroad, as a particular
     place where two streets intersect.

You can also find documents that use term *geospatial feature* to refer
to geographic features.

*Geometry* is another word that denotes a geographic feature.  The
original meaning of the word *geometry* denotes a branch of mathematics.
Another meaning comes from cartography, referring to the geometric
features that cartographers use to map the world.

This chapter uses all of these terms synonymously: *geographic
feature*, *geospatial feature*, *feature*, or *geometry*.  The term
most commonly used here is *geometry*.

Let's define a *geometry* as _a point or an aggregate of points
representing anything in the world that has a location_.

[Назад] [Содержание] [Вперед]