18.1. Introduction to MySQL Spatial Support
MySQL implements spatial extensions following the specification of
the Open Geospatial 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
In 1997, the Open Geospatial Consortium published the
OpenGIS® 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 OGC Web site at
http://www.opengis.org/docs/99-049.pdf. 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 specification describe a set
of SQL geometry types, as well as functions on those types to
create and analyze 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.
Some documents use the term geospatial
feature to refer to geographic features.
Geometry is another word that
denotes a geographic feature. Originally the word
geometry meant measurement of the
earth. 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:
geometry. Here, the term most
commonly used is geometry,
defined as a point or an aggregate of points
representing anything in the world that has a location.