12.15.2 Argument Handling by Spatial Functions

Spatial values, or geometries, have the properties described at Section, “Geometry Class”. The following discussion lists general spatial function argument-handling characteristics. Specific functions or groups of functions may have additional argument-handling characteristics, as discussed in the sections where those function descriptions occur.

Spatial functions are defined only for valid geometry values. If an invalid geometry is passed to a spatial function, the result is undefined.

The Spatial Reference Identifier (SRID) of a geometry identifies the coordinate space in which the geometry is defined. In MySQL, the SRID value is an integer associated with the geometry value. However, all calculations are done assuming SRID 0, representing cartesian (planar) coordinates, regardless of the actual SRID value. In the future, calculations may use the specified SRID values. To ensure SRID 0 behavior, create geometries using SRID 0. SRID 0 is the default for new geometries if no SRID is specified.

The maximum usable SRID value is 232−1. If a larger value is given, only the lower 32 bits are used.

Geometry values produced by any spatial function inherit the SRID of the geometry arguments.