Condition true for a period of time

Question

I am producing a report where one of the conditions to detect is if a tag is above a certain value for a consecutive period of time. I've loosely nutted out what I need to know, but am unsure of the correct direction to head in with it.
My thoughts are:
I have raw data for Turbidity
Query it at one minute samples over a one day period
Detect a sample of over 0.1 NTU
If 15+ consecutive samples are over 0.1 NTU flag it as a non-compliance (Boolean?)
Count the number of unique non-compliances (Integer?)
Ideally this would be a query which would return the bool and int and take date start and date end (i.e. four parameters)
AnyAny help would be much appreciated.
ChCheers,
Chris

Answer 1

Hi deltahfturbo,
According to your description, you want to use a query to get the total non-compliance samples and the status of samples (compliance or not) with date start and end. Right?
In this scenario, we can use case when statement in your query to return true/false the amount of non-compliance samples exceeds 15. Please refer to query below:
declare @startdate date
set @startdate='2014/1/1'
declare @enddate date
set @enddate='2014/1/7'
select sum(
case when [NTU]>0.2 THEN 1
else 0
end
) as sample,
case when sum(
case when [NTU]>0.2 THEN 1
else 0
end
)>15 then 'non-compliance '
else 'compliance'
end
) as status,
@startdate as StartDate,
@enddate as EndDate
from [table]
where CreateDate>@startdate and CreateDate<@enddate
If you still have any question, please feel free to ask.
Best Regards,
Simon Hou