sql query question ?

Hi All,

I have a table called 

vehicle_duty_cycle_summary 


vehicle_master_id | starting_odometer |
ending_odometer |         login_time         |       
logout_time
-------------------+-------------------+-----------------+----------------------------+----------------------------

4 |          53379.00 |        53504.00 | 2006-12-19
16:19:16.584547 | 2006-12-20 07:12:57.716907                4 |          51310.00 |       
51457.00 | 2006-12-05 16:04:51.585441 | 2006-12-06
07:18:10.251535                4 |          42411.00 |       
42411.00 | 2006-09-14 16:03:49.541442 | 2006-09-15
08:24:41.308339                4 |          54012.00 |       
54146.00 | 2006-12-25 16:14:31.313728 | 2006-12-26
07:05:55.82487                4 |          43071.00 |       
43181.00 | 2006-09-21 11:24:43.466766 | 2006-09-22
07:10:09.362792                4 |          51208.00 |       
51305.00 | 2006-12-04 16:14:14.600105 | 2006-12-05
08:03:38.139832                4 |          50235.00 |       
50370.00 | 2006-11-27 15:55:48.866925 | 2006-11-28
07:27:25.898991                4 |          53231.00 |       
53362.00 | 2006-12-18 16:06:42.764133 | 2006-12-19
07:06:03.450072                4 |          52656.00 |       
52818.00 | 2006-12-13 16:03:47.189303 | 2006-12-14
07:59:11.463733                4 |          50801.00 |       
50880.00 | 2006-12-02 16:03:55.666321 | 2006-12-03
06:53:21.433746                9 |          85360.00 |       
85493.00 | 2007-06-10 07:17:12.330974 | 2007-06-10
22:11:04.422656                9 |          78009.00 |       
78042.00 | 2007-03-12 17:53:18.794001 | 2007-03-12
20:42:39.439647                9 |          84529.00 |       
84679.00 | 2007-06-01 06:42:09.306306 | 2007-06-01
20:35:54.317172                9 |          78058.00 |       
78149.00 | 2007-03-13 10:08:48.696709 | 2007-03-13
21:50:31.136412                9 |          86506.00 |       
86595.00 | 2007-06-21 09:28:40.504082 | 2007-06-21
23:15:41.862292                9 |          78155.00 |       
78239.00 | 2007-03-14 09:32:58.512817 | 2007-03-14
20:58:24.36362                9 |          84894.00 |       
85012.00 | 2007-06-04 07:59:00.896969 | 2007-06-04
18:42:13.791974                9 |          78435.00 |       
78494.00 | 2007-03-16 07:48:23.626402 | 2007-03-16
21:39:09.479043                9 |          83992.00 |       
84045.00 | 2007-05-25 07:25:20.462928 | 2007-05-25
21:23:43.697577                9 |          78506.00 |       
78595.00 | 2007-03-17 08:01:06.003564 | 2007-03-17
19:48:32.383689                9 |          85493.00 |       
85640.00 | 2007-06-11 06:58:03.052538 | 2007-06-11
22:56:13.134053                9 |          78279.00 |       
78395.00 | 2007-03-15 08:00:58.198265 | 2007-03-15
21:39:00.052173


I would like to compute the following on this table.

Idle time of vehicel=(ending_odometer reading of the
previous day -   
starting_odometer reading of the present day) for
every vehicle

can anybody help me this issue.

Thanks in advance.

Trilok






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