如何使用 JDBC 从两个不同的 MySQL 数据库中检索数据？

Question

如何使用 jdbc 在单个查询中从两个不同的 MySQL 数据库中检索数据？

SELECT 
      a.`driver_id`,
      a.`state`, 
      a.`lat`, 
      a.`long`, 
      MAX(a.`time_stamp`) AS timestamp,
      b.vehicle_type 
 FROM `rl_driv_location` AS a, `rl_driver_info` AS b 
 WHERE a.`state` = 1 AND a.`driver_id` = b.`user_id` 
       AND b.`vehicle_type` = '"+ cartype +"'  
 GROUP BY driver_id

• 具有rl_driv_location 表的位置数据库。
• 具有rl_driver_info 表的核心数据库。

Answer 1

只需指定要检索数据的数据库的名称。见下文。

SELECT 
      a.`driver_id`,
      a.`state`, 
      a.`lat`, 
      a.`long`, 
      MAX(a.`time_stamp`) AS timestamp,
      b.vehicle_type 
 FROM location.`rl_driv_location` AS a, core.`rl_driver_info` AS b 
 WHERE a.`state` = 1 AND a.`driver_id` = b.`user_id` 
       AND b.`vehicle_type` = '"+ cartype +"'  
 GROUP BY driver_id