I have a table that contains the following:
DataDate Value
2010-03-01 08:31:32.000 100
2010-03-01 08:31:40.000 110
2010-03-01 08:31:42.000 95
2010-03-01 08:31:45.000 101
. .
. .
. .
I need to multiply the value column by the difference in time between the current and previous rows and sum that for the entire day.
I currently have the data set up to come in every 10 seconds which makes for a simple conversion in the query:
SELECT Sum((Value/6) FROM History WHERE DataDate BETWEEN @startDate and @endDate
Where @startDate and @endDate are today's date at 00:00:00 and 11:59:59.
Before I set the data to be collected every 10 seconds it was collected whenever the Value changed. There aren't any duplicate entries in terms of time, the minimum time difference is 1 second.
How can I set up a query to get the elapsed time between rows for the case when I don't know the time interval between readings?
I am using SQL Server 2005.
WITH rows AS
(
SELECT *, ROW_NUMBER() OVER (ORDER BY DataDate) AS rn
FROM mytable
)
SELECT DATEDIFF(second, mc.DataDate, mp.DataDate)
FROM rows mc
JOIN rows mp
ON mc.rn = mp.rn - 1
In SQL Server 2012+:
SELECT DATEDIFF(second, pDataDate, dataDate)
FROM (
SELECT *,
LAG(dataDate) OVER (ORDER BY dataDate) pDataDate
FROM rows
) q
WHERE pDataDate IS NOT NULL