MySQL 8.0 Reference Manual Including MySQL NDB Cluster 8.0

11.5.5 Spatial Reference System Support

A spatial reference system (SRS) for spatial data is a coordinate-based system for geographic locations.

There are different types of spatial reference systems:

MySQL maintains information about available spatial reference systems for spatial data in the data dictionary mysql.st_spatial_reference_systems table, which can store entries for projected and geographic SRSs. This data dictionary table is invisible, but SRS entry contents are available through the INFORMATION_SCHEMA ST_SPATIAL_REFERENCE_SYSTEMS table, implemented as a view on mysql.st_spatial_reference_systems (see Section 25.28, “The INFORMATION_SCHEMA ST_SPATIAL_REFERENCE_SYSTEMS Table”).

The following example shows what an SRS entry looks like:

mysql> SELECT *
       FROM INFORMATION_SCHEMA.ST_SPATIAL_REFERENCE_SYSTEMS
       WHERE SRS_ID = 4326\G
*************************** 1. row ***************************
                SRS_NAME: WGS 84
                  SRS_ID: 4326
            ORGANIZATION: EPSG
ORGANIZATION_COORDSYS_ID: 4326
              DEFINITION: GEOGCS["WGS 84",DATUM["World Geodetic System 1984",
                          SPHEROID["WGS 84",6378137,298.257223563,
                          AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],
                          PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],
                          UNIT["degree",0.017453292519943278,
                          AUTHORITY["EPSG","9122"]],
                          AXIS["Lat",NORTH],AXIS["Long",EAST],
                          AUTHORITY["EPSG","4326"]]
             DESCRIPTION:

This entry describes the SRS used for GPS systems. It has a name (SRS_NAME) of WGS 84 and an ID (SRS_ID) of 4326, which is the ID used by the European Petroleum Survey Group (EPSG).

SRS definitions in the DEFINITION column are WKT values, represented as specified in the Open Geospatial Consortium document OGC 12-063r5.

SRS_ID values represent the same kind of values passed as the SRID argument to spatial functions. SRID 0 (the unitless Cartesian plane) is special. It is always a legal spatial reference system ID and can be used in any computations on spatial data that depend on SRID values.

For computations on multiple geometry values, all values must have the same SRID or an error occurs.

SRS definition parsing occurs on demand when definitions are needed by GIS functions. Parsed definitions are cached in the data dictionary cache so that parsing overhead is not incurred for every statement that needs SRS information.

To enable manipulation of SRS entries stored in the data dictionary, MySQL provides these SQL statements: