ST_SPATIAL_REFERENCE_SYSTEMS 表提供有关空间数据可用空间参考系统（SRS）的信息。此表基于 SQL/MM（ISO/IEC 13249-3）标准。The ST_SPATIAL_REFERENCE_SYSTEMS table provides information about available spatial reference systems (SRSs) for spatial data. This table is based on the SQL/MM (ISO/IEC 13249-3) standard.

ST_SPATIAL_REFERENCE_SYSTEMS 表中的条目基于 欧洲石油勘测组（EPSG）数据集，除了 SRID 0，它对应于 MySQL 中使用的特殊 SRS，表示一个无限平面笛卡尔坐标系，其轴没有分配单位。有关 SRS 的更多信息，请参阅 第 13.4.5 节，“空间参考系统支持”。Entries in the ST_SPATIAL_REFERENCE_SYSTEMS table are based on the European Petroleum Survey Group (EPSG) data set, except for SRID 0, which corresponds to a special SRS used in MySQL that represents an infinite flat Cartesian plane with no units assigned to its axes. For additional information about SRSs, see Section 13.4.5, “Spatial Reference System Support”.

ST_SPATIAL_REFERENCE_SYSTEMS 表包含以下列：The ST_SPATIAL_REFERENCE_SYSTEMS table has these columns:

说明Notes

示例Example

mysql> SELECT * FROM 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:

此条目描述了用于 GPS 系统的 SRS。它的名称（SRS_NAME）为 WGS 84，ID（SRS_ID）为 4326，这是由欧洲石油测量组（EPSG）使用的 ID。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).

投影和地理 SRS 的 DEFINITION 值分别以 PROJCS 和 GEOGCS 开头。SRID 为 0 的定义是特殊的，其 DEFINITION 值为空。以下查询根据 DEFINITION 值确定 ST_SPATIAL_REFERENCE_SYSTEMS 表中分别有多少条目对应投影、地理和其他 SRS：The DEFINITION values for projected and geographic SRSs begin with PROJCS and GEOGCS, respectively. The definition for SRID 0 is special and has an empty DEFINITION value. The following query determines how many entries in the ST_SPATIAL_REFERENCE_SYSTEMS table correspond to projected, geographic, and other SRSs, based on DEFINITION values:

mysql> SELECT
         COUNT(*),
         CASE LEFT(DEFINITION, 6)
           WHEN 'PROJCS' THEN 'Projected'
           WHEN 'GEOGCS' THEN 'Geographic'
           ELSE 'Other'
         END AS SRS_TYPE
       FROM INFORMATION_SCHEMA.ST_SPATIAL_REFERENCE_SYSTEMS
       GROUP BY SRS_TYPE;
+----------+------------+
| COUNT(*) | SRS_TYPE   |
+----------+------------+
|        1 | Other      |
|     4668 | Projected  |
|      483 | Geographic |
+----------+------------+

为了能够操作存储在数据字典中的 SRS 条目，MySQL 提供了以下 SQL 语句：To enable manipulation of SRS entries stored in the data dictionary, MySQL provides these SQL statements: