获取设备组中的最新传感器值

Question

我有一个包含以下架构的表：

meshSetVersion integer
gatewayMAC text
deviceMAC text
sensorID integer
sensorValue text
timestamp time

首先，我找到最新的meshSetVersion：

(select max(meshSetVersion) from test where gatewayMAC='XXX') as lastV

然后我发现它的设备：

select distinct gatewayMAC, deviceMAC from test
where gatewayMAC='xxx' and meshSetVersion=lastV

然后我需要按时间戳

获取每个ID的最新sensorValue

Answer 1

一种方法使用distinct on。我认为这是你想要的逻辑：

select distinct on (sensorId) t.*
from test t
where t.meshSetVersion = (select max(t2.meshSetVersion)
                          from test t2
                          where t2.gatewayMach = 'xxx'
                         )
order by sensorId, timestamp desc;