Select only record until timestamp from another table - sql

Question

I have three tables.
The first one is Device table
+----------+------+
| DeviceId | Type |
+----------+------+
| 1 | 10 |
| 2 | 20 |
| 3 | 30 |
+----------+------+
The second one is History table - data received by different devices.
+----------+-------------+--------------------+
| DeviceId | Temperature | TimeStamp |
+----------+-------------+--------------------+
| 1 | 31 | 15.08.2020 1:42:00 |
| 2 | 100 | 15.08.2020 1:42:01 |
| 2 | 40 | 15.08.2020 1:43:00 |
| 1 | 32 | 15.08.2020 1:44:00 |
| 1 | 34 | 15.08.2020 1:45:00 |
| 3 | 20 | 15.08.2020 1:46:00 |
| 2 | 45 | 15.08.2020 1:47:00 |
+----------+-------------+--------------------+
The third one is DeviceStatusHistory table
+----------+---------+--------------------+
| DeviceId | State | TimeStamp |
+----------+---------+--------------------+
| 1 | 1(OK) | 15.08.2020 1:42:00 |
| 2 | 1(OK) | 15.08.2020 1:43:00 |
| 1 | 1(OK) | 15.08.2020 1:44:00 |
| 1 | 0(FAIL) | 15.08.2020 1:44:30 |
| 1 | 0(FAIL) | 15.08.2020 1:46:00 |
| 2 | 0(FAIL) | 15.08.2020 1:46:10 |
+----------+---------+--------------------+
I want to select the last temperature of devices, but take into account only those history records that occurs until the first device failure.
Since device1 starts failing from 15.08.2020 1:44:30, I don't want its records that go after that timestamp.
The same for the device2.
So as a final result, I want to have only data of all devices until they get first FAIL status:
+----------+-------------+--------------------+
| DeviceId | Temperature | TimeStamp |
+----------+-------------+--------------------+
| 2 | 40 | 15.08.2020 1:43:00 |
| 1 | 32 | 15.08.2020 1:44:00 |
| 3 | 20 | 15.08.2020 1:46:00 |
+----------+-------------+--------------------+
I can select an appropriate history only if device failed at least once:
SELECT * FROM Device D
CROSS APPLY
(SELECT TOP 1 * FROM History H
WHERE D.Id = H.DeviceId
and H.DeviceTimeStamp <
(select MIN(UpdatedOn) from DeviceStatusHistory Y where [State]=0 and DeviceId=D.Id)
ORDER BY H.DeviceTimeStamp desc) X
ORDER BY D.Id;
The problems is, if a device never fails, I don't get its history at all.
Update:
My idea is to use something like this
SELECT * FROM DeviceHardwarePart HP
CROSS APPLY
(SELECT TOP 1 * FROM History H
WHERE HP.Id = H.DeviceId
and H.DeviceTimeStamp <
(select ISNULL((select MIN(UpdatedOn) from DeviceMetadataPart where [State]=0 and DeviceId=HP.Id),
cast('12/31/9999 23:59:59.997' as datetime)))
ORDER BY H.DeviceTimeStamp desc) X
ORDER BY HP.Id;
I'm not sure whether it is a good solution

Answer 1

You can use COALESCE: coalesce(min(UpdateOn), cast('9999-12-31 23:59:59' as datetime)). This ensures you always have an upperbound for your select instead of NULL.

Answer 2

I will treat this as two parts problem
I will try to find the time at which device has failed and if it hasn't failed I will keep it as a large value like some timestamp in 2099
Once I have the above I can simply join with histories table and take the latest value before the failed timestamp.
In order to get one, I guess there can be several approaches. From top of my mind something like below should work
select device_id, coalesce(min(failed_timestamps), cast('01-01-2099 01:01:01' as timestamp)) as failed_at
(select device_id, case when state = 0 then timestamp else null end as failed_timestamps from History) as X
group by device_id
This gives us the minimum of failed timestamp for a particular device, and an arbitrary large value for the devices which have never failed.
I guess after this the solution is straight forward.