[英]Getting latest sensor value in set of devices
I have a table with following schema: 我有一个具有以下架构的表:
meshSetVersion integer
gatewayMAC text
deviceMAC text
sensorID integer
sensorValue text
timestamp time
First I find the latest meshSetVersion with: 首先,我找到最新的meshSetVersion:
(select max(meshSetVersion) from test where gatewayMAC='XXX') as lastV
Then I find it's devices: 然后我发现它是设备:
select distinct gatewayMAC, deviceMAC from test
where gatewayMAC='xxx' and meshSetVersion=lastV
Then I need to get latest sensorValue of each ID by timestamp 然后我需要通过时间戳获取每个ID的最新sensorValue
One method uses distinct on
. 一种方法
distinct on
使用distinct on
。 I think this is the logic that you want: 我认为这是您想要的逻辑:
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;
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