T-SQL DateDiff - partition by "full hours ago", rather than "times minutes turned 00 since"

Question

I have a table with timestamps, and I want to partition this table into hour-long intervals, starting at now and going backwards a couple of hours. I'm unable to get the results I need with the T-SQL DATEDIFF function, since it counts the number of times the minute hand passes 12 between the two dates - I want the number of times them minute hand passes where it is now between the timestamp and now.

Is there a straightforward way to do this in T-SQL?

Update: In response to comments, here's some sample data, the query I'm currently using and the results I'm getting, as well as the results I want.

Sample data:

TimeStamp
*********
2010-07-20 11:00:00.000
2010-07-20 10:44:00.000
2010-07-20 10:14:00.000
2010-07-20 11:00:00.000
2010-07-20 11:40:00.000
2010-07-20 10:16:00.000
2010-07-20 13:00:00.000
2010-07-20 12:58:00.000

Current query:

SELECT TimeStamp, DATEDIFF(HOUR, TimeStamp, CURRENT_TIMESTAMP) AS Diff FROM ...

Results:

    TimeStamp                   Diff
    *********                   ****
    2010-07-20 11:00:00.000     2
    2010-07-20 10:44:00.000     3
    2010-07-20 10:14:00.000     3
    2010-07-20 11:00:00.000     2
    2010-07-20 11:40:00.000     2
    2010-07-20 10:16:00.000     3
    2010-07-20 13:00:00.000     0
    2010-07-20 12:58:00.000     1

What I'd rather have:

    -- The time is now, for the sake of the example, 13:40

    TimeStamp                   Diff
    *********                   ****
    2010-07-20 11:00:00.000     3 -- +1
    2010-07-20 10:44:00.000     3
    2010-07-20 10:14:00.000     4 -- +1
    2010-07-20 11:00:00.000     3 -- +1
    2010-07-20 11:40:00.000     2 or 3 -- edge case, I don't really care which
    2010-07-20 10:16:00.000     4 -- +1
    2010-07-20 13:00:00.000     1 -- +1
    2010-07-20 12:58:00.000     1

I've marked the results that changed with a +1. Also, I don't really care if this is 0-indexed or 1-indexed, but basically, if it's now 13:40 I want the time spans that get the same value to be

    12:40-13:40    1 (or 0)
    11:40-12:40    2 (or 1)
    10:40-11:40    3 (or 2)
    09:40-10:40    4 (or 3)

Answer 1

Can you not just use DATEDIFF(minute,.. and then divide the result by 60 and take the integer value. e.g.

 SELECT DATEDIFF(minute, '2010-07-20 06:00', GETDATE())/60

I believe this will be implicitly cast as an int as datediff returns an int, it gives whole hours with no rounding.

To use your exact query from your updated post:

SELECT TimeStamp, (DATEDIFF(minute, TimeStamp, CURRENT_TIMESTAMP) /60) AS Diff FROM ...