MySQL Manual
11 Spatial Extensions in MySQL
11.1 Introduction
MySQL implements spatial extensions following the specification of
the Open GIS Consortium (OGC). This is an international consortium
of more than 250 companies, agencies, and universities participating
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/.
In 1997, the Open GIS Consortium published the OpenGIS (R) Simple Features Specifications For SQL, a document that proposes several conceptual ways for extending an SQL RDBMS to support spatial data. This specification is available from the Open GIS web site at http://www.opengis.org/techno/implementation.htm. 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.
