Question

I have a table which looks like this:

 . |  ID  | SystemID |       StartDateTime       |        EndDateTime        |
1 |  24  |     1    |  2012-11-09 13:59:00.000  |  2012-11-09 14:23:00.000  |
2 |  25  |     2    |  2012-11-09 13:59:00.000  |  2012-11-09 14:23:00.000  |
3 |  26  |     3    |  2012-11-09 14:00:00.000  |  2012-11-09 14:24:00.000  |
4 |  27  |     1    |  2012-11-09 16:20:00.000  |  2012-11-09 17:19:00.000  |
5 |  28  |     2    |  2012-11-09 16:21:00.000  |  2012-11-09 17:37:00.000  |
6 |  29  |     3    |  2012-11-09 17:25:00.000  |  2012-11-09 17:50:00.000  |

For each system id, I want to select the row that ended closest to and before a given time.
For example if the time was 17:30, the result would look like this:

|  ID  | SystemID |       StartDateTime       |        EndDateTime        |
|  27  |     1    |  2012-11-09 16:20:00.000  |  2012-11-09 17:19:00.000  |
|  25  |     2    |  2012-11-09 13:59:00.000  |  2012-11-09 14:23:00.000  |
|  26  |     3    |  2012-11-09 14:00:00.000  |  2012-11-09 14:24:00.000  |

Hope this makes sense! Thanks for your help.

Answer 1

You could use outer apply:

select  *
from    (
        select  distinct SystemID
        from    Table1
        ) as ids
outer apply
        (
        select  top 1 *
        from    Table1 t1
        where   t1.SystemID = ids.SystemID
                and t1.EndDateTime < '2012-11-09 17:30'
        order by
                t1.EndDateTime desc
        ) as last

Live example at SQL Fiddle.