I think I'm missing something here but for what it's worth:
WITH SampleData (start_time, end_time) AS (
SELECT '22:00', '05:59'
UNION ALL SELECT '12:00', '18:59'
)
SELECT start_time, end_time
,ElapsedMin=
CASE WHEN st > et
THEN 1440-DATEDIFF(minute, et, st)
ELSE DATEDIFF(minute, st, et)
END
FROM SampleData a
CROSS APPLY (SELECT st=CAST(start_time AS TIME), et=CAST(end_time AS TIME)) b;
Note: The CROSS APPLY is not even necessary. I only included it to show explicitly the CAST that would occur implicitly anyway.
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