Question

I need to copy each row as many times as how many hours there are between StartTime and EndTime.

Example data:

SQLFIDDLEExample

TimeKey HourKey SensorKey   IdleTimeMinute  StartTime   EndTime
20121017    8   45  110 2012.10.17 08:31    2012.10.17 10:21
20121017    10  45  25  2012.10.17 10:26    2012.10.17 10:51
20121017    12  45  5   2012.10.17 12:21    2012.10.17 12:26
20121017    12  45  60  2012.10.17 12:41    2012.10.17 13:41
20121017    13  45  55  2012.10.17 13:51    2012.10.17 14:46
20121017    15  45  5   2012.10.17 15:11    2012.10.17 15:16
20121017    15  45  35  2012.10.17 15:46    2012.10.17 16:21
20121017    18  45  5   2012.10.17 18:51    2012.10.17 18:56

Explanation

For example, the first row spans the hours 8, 9, and 10. In each of the three output rows, IdleTimeMinute needs to be the minutes duration within that hour.

Expected Result:

TimeKey HourKey SensorKey   IdleTimeMinute  StartTime   EndTime
20121017    8   45  29  2012.10.17 08:31    2012.10.17 10:21
20121017    9   45  60  2012.10.17 08:31    2012.10.17 10:21
20121017    10  45  21  2012.10.17 08:31    2012.10.17 10:21
20121017    10  45  25  2012.10.17 10:26    2012.10.17 10:51
20121017    12  45  5   2012.10.17 12:21    2012.10.17 12:26
20121017    12  45  19  2012.10.17 12:41    2012.10.17 13:41
20121017    13  45  41  2012.10.17 12:41    2012.10.17 13:41
20121017    13  45  9   2012.10.17 13:51    2012.10.17 14:46
20121017    14  45  46  2012.10.17 13:51    2012.10.17 14:46
20121017    15  45  5   2012.10.17 15:11    2012.10.17 15:16
20121017    15  45  14  2012.10.17 15:46    2012.10.17 16:21
20121017    16  45  21  2012.10.17 15:46    2012.10.17 16:21
20121017    18  45  5   2012.10.17 18:51    2012.10.17 18:56

Smaller Example

Smaller example from first two lines:

TimeKey HourKey SensorKey   IdleTimeMinute  StartTime   EndTime
20121017    8   45  110 2012.10.17 08:31    2012.10.17 10:21
20121017    10  45  25  2012.10.17 10:26    2012.10.17 10:51

For first line we have time 8:31 - 10:21 so In 8 Hour 29 Minutes, In 9 Hour 60 Minutes, In 10 Hour 21 Minute.

Expected small result:

TimeKey HourKey SensorKey   IdleTimeMinute  StartTime   EndTime
20121017    8   45  29  2012.10.17 08:31    2012.10.17 10:21
20121017    9   45  60  2012.10.17 08:31    2012.10.17 10:21
20121017    10  45  21  2012.10.17 08:31    2012.10.17 10:21
20121017    10  45  25  2012.10.17 10:26    2012.10.17 10:51

Answer 1

Here you go. This will handle even cases where the span of time passes midnight or goes over many days. It should perform very well.

See the SqlFiddle for it.

DECLARE @MaxHour int = IsNull((SELECT Max(DateDiff(hour, StartTime, EndTime)) + 1 FROM dbo.Table1), 0);

WITH L0 AS (SELECT 1 N UNION ALL SELECT 1),
L1 AS (SELECT 1 N FROM L0, L0 B),
L2 AS (SELECT 1 N FROM L1, L1 B),
L3 AS (SELECT 1 N FROM L2, L2 B),
L4 AS (SELECT 1 N FROM L3, L3 B),
L5 AS (SELECT 1 N FROM L4, L4 B),
Nums AS (SELECT Num = Row_Number() OVER (ORDER BY (SELECT 1)) FROM L5)
SELECT
   TimeKey = Convert(int, Convert(char(8), S.HourStartTime, 112)),
   HourKey = DatePart(hour, S.HourStartTime),
   T.SensorKey,
   IdleTimeMinute = DateDiff(minute, S.HourStartTime, E.HourEndTime),
   T.StartTime,
   T.EndTime,
   S.HourStartTime,
   E.HourEndTime
FROM
   dbo.Table1 T
   CROSS APPLY (
      SELECT AnchorHour = DateAdd(hour, DateDiff(hour, 0, T.StartTime) + N.Num - 1, 0)
      FROM Nums N
      WHERE
         DateDiff(hour, T.StartTime, T.EndTime) + 1 >= N.Num
         AND N.Num <= @MaxHour
   ) D
   CROSS APPLY (
      SELECT HourStartTime = Max(StartTime)
      FROM (VALUES (D.AnchorHour), (T.StartTime)) S (StartTime)
   ) S
   CROSS APPLY (
      SELECT HourEndTime = Min(EndTime)
      FROM (VALUES (DateAdd(hour, 1, D.AnchorHour)), (T.EndTime)) E (EndTime)
   ) E
ORDER BY
   TimeKey,
   StartTime,
   HourKey;

I included the new timespan for the selected hour. If you want that timespan to end at :59 instead of :00 of the next hour, then in the third CROSS APPLY change DateAdd(hour, 1, D.AnchorHour) to DateAdd(minute, 59, D.AnchorHour) and add + 1 to the end of DateDiff(minute, S.HourStartTime, E.HourEndTime) in the SELECT clause.

In my opinion:

• Using a CTE to incrementally add one’s way up to the max difference is not optimal. The CTE I use bails out close to as soon as the max Num is reached, and can go up to 4294967296.
• Solutions that don’t calculate the new TimeKey are fragile due to depending on an unstated assumption that midnight cannot be crossed.
• Solutions that depend on you changing your table to have a monotonically-increasing ID with no gaps are unlikely to fit your real-world data.

Note: the reason I declare the @MaxHour variable is that the on-the-fly numbers table CTE I’m using wants a constant. Well, that’s not exactly accurate, but the long and short of it is that without a constant it can choose an execution plan that doesn’t limit the rows in the place needed to get a speedy query. I chose DateDiff to compute this, but in fact I see now that this would probably be faster, and definitely would be faster if you have an index on IdleTimeMinute:

DECLARE @MaxHour int = IsNull((SELECT (Max(IdleTimeMinute) + 118) / 60 FROM dbo.Table1), 0);

Since the smallest time range that can span two different hours is 2 minutes (say 11:59 to 12:00) then we have to add 118 minutes to be sure to get at least 2 hours out of it.