Calculating time between entries

[llitvin]

I have a table where a start time and stop time are recorded for a particular piece of equipment. There are 3 pieces of equipment that are selectable on the record. I would like to calculate the down-time for each piece of equipment (the duration between the stop time and the start time).



I appreciate any suggestions. Thank you.

[June7]

Are start and stop times in same or separate records?

Provide sample data.

[llitvin]

Each record has a start and stop time. I would like to know the time difference between "record 1" stop time and "record 2" start time for the same reactor. Here is some sample data that you requested. Using the data as an example, I would like to calculate the difference between the two red highlighted cells.

Reactor	Start Date/Time	Stop Date/Time
1	6/27/2013 21:53	7/3/13 12:24 AM
3	7/1/2013 16:45	7/3/13 4:05 PM
2	7/2/2013 14:48	7/4/13 9:57 PM
1	7/3/2013 0:33	7/8/13 11:13 AM
3	7/4/2013 10:41	7/9/13 11:40 AM
2	7/4/2013 22:59	7/11/13 1:51 AM
1	7/8/2013 16:24	7/10/13 1:34 AM
3	7/9/2013 13:47	7/11/13 9:23 AM
1	7/10/2013 3:00	7/12/13 12:40 AM
2	7/11/2013 2:06	7/16/13 8:45 PM
3	7/11/2013 21:10	7/17/13 11:09 AM
1	7/16/2013 23:37	7/18/13 5:46 AM

Thank you for your help.

[June7]

Getting value from another record of same table is tricky. Use a subquery. Review http://allenbrowne.com/subquery-01.html#AnotherRecord

A DMax() might also accomplish but domain aggregate functions can cause a query to run slow, especially on a large dataset.