我正在尝试编写一个查询，该查询从GPSReport表返回每个唯一设备的最新GPS位置。表中有50个设备，所以我只希望返回50行。
这是我到目前为止（无法正常工作）
SELECT TOP(SELECT COUNT(DISTINCT device_serial) FROM GPSReport) * FROM GPSReport AS G1 RIGHT JOIN (SELECT DISTINCT device_serial FROM GPSReport) AS G2 ON G2.device_serial = G1.device_serial ORDER BY G2.device_serial, G1.datetime DESC
这将返回50行，但不会为每个device_serial返回唯一的行。它返回第一个设备的所有报告，然后返回第二个设备的所有报告，依此类推。
我要在一个查询中执行的操作是否可行？
SELECT * FROM GPSReport AS G1 JOIN (SELECT device_serial, max(datetime) as mostrecent FROM GPSReport group by device_serial) AS G2 ON G2.device_serial = G1.device_serial and g2.mostrecent = g1.datetime ORDER BY G1.device_serial
