SELECT DeviceId, CAST(ROUND(AVG(distance / time_diff), 5, 1) AS decimal(18,5)) AS '移动速率' FROM ( SELECT t1.DeviceId, t1.StartTime, t1.V1, t1.V2, t1.V3, DATEDIFF(SECOND, t2.StartTime, t1.StartTime) AS time_diff, SQRT(POWER(t1.V1 - t2.V1, 2) + POWER(t1.V2 - t2.V2, 2) + POWER(t1.V3 - t2.V3, 2)) AS distance FROM T_BMWY_ResolveDeviceData t1 JOIN T_BMWY_ResolveDeviceData t2 ON t1.DeviceId = t2.DeviceId AND t1.StartTime > t2.StartTime WHERE t1.StartTime >= DATEADD(DAY, -5, GETDATE()) ) t WHERE time_diff > 0 GROUP BY DeviceId 优化一下查询速度

可以考虑在WHERE子句中添加一些限制条件来减少查询的数据量。例如，可以根据DeviceId和StartTime将T_BMWY_ResolveDeviceData表分为多个分区，并对查询进行分区限制，只查询最近几天的数据。同时，可以考虑使用索引来加快查询速度。

以下是一个优化后的查询语句：

SELECT DeviceId, CAST(ROUND(AVG(distance / time_diff), 5, 1) AS decimal(18,5)) AS '移动速率' 
FROM (
    SELECT t1.DeviceId, t1.StartTime, t1.V1, t1.V2, t1.V3,
           DATEDIFF(SECOND, t2.StartTime, t1.StartTime) AS time_diff,
           SQRT(POWER(t1.V1 - t2.V1, 2) + POWER(t1.V2 - t2.V2, 2) + POWER(t1.V3 - t2.V3, 2)) AS distance
    FROM T_BMWY_ResolveDeviceData t1
    JOIN T_BMWY_ResolveDeviceData t2 ON t1.DeviceId = t2.DeviceId AND t1.StartTime > t2.StartTime
    WHERE t1.StartTime >= DATEADD(DAY, -5, GETDATE())
      AND t1.StartTime >= '2021-01-01' -- 限制查询的起始时间
      AND t1.DeviceId BETWEEN 1 AND 1000 -- 限制查询的DeviceId范围
) t 
WHERE time_diff > 0 
GROUP BY DeviceId;

此外，还可以考虑使用分页查询，每次只查询部分结果，减少单次查询的数据量。例如，可以使用ROW_NUMBER()函数进行分页查询。