MySQL 在多个设备上检查上次更新时间

Question

我想检查每个 treehugger id (TreeHuggerId) 的上次更新日期和时间 (recordTime)，下面是我所做的。根据以下查询，输出不是最后更新时间。请指教。谢谢。

 SELECT `recordTime`, DISTINCT `TreeHuggerId` FROM `SENSOR_TREEHUGGERS`
 WHERE `TreeHuggerId` < 20000 and `TreeHuggerId` > 10000
 ORDER BY `recordTime` desc

Answer 1

您必须为每个 TreeHuggerId 选择 MAX(recordTime)，并且不需要不同

SELECT TreeHuggerId,MAX(recordTime) FROM SENSOR_TREEHUGGERS

最后

GROUP BY TreeHuggerId

像这样

SELECT TreeHuggerId,MAX(recordTime) FROM SENSOR_TREEHUGGERS
WHERE TreeHuggerId BETWEEN 10000 AND 20000
GROUP BY TreeHuggerId