Recursion is not needed here if this is really being done in SQL 2012.
SELECT MACHINE_NUMBER, VALUE, EVENT_DATE
FROM
(
SELECT *
,s=DATEDIFF(second
,EVENT_DATE
,LEAD(EVENT_DATE, 1) OVER (PARTITION BY MACHINE_NUMBER ORDER BY EVENT_DATE))
FROM #MACHINE_LOG
) a
WHERE s >= 15;
Note that I had to use second in DATEDIFF because the EVENT_DATEs in your data are separated by seconds and not minutes.
My thought question: Have you ever been told that your query runs too fast?
My advice:
INDEXing a poor-performing query is like putting sugar on cat food. Yeah, it probably tastes better but are you sure you want to eat it?
The path of least resistance can be a slippery slope. Take care that fixing your fixes of fixes doesn't snowball and end up costing you more than fixing the root cause would have in the first place.
Need to UNPIVOT? Why not CROSS APPLY VALUES instead?[/url]
Since random numbers are too important to be left to chance, let's generate some![/url]
Learn to understand recursive CTEs by example.[/url]
[url url=http://www.sqlservercentral.com/articles/St