Home/ Questions/Q 8125875
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-06T06:57:47+00:00

I’ve got a table in an Oracle 11g database that is similar to the

  • 0

I’ve got a table in an Oracle 11g database that is similar to the following:

process_times:
--------------------------------------------
machine_id | load_id | start_time | end_time

some example records might look like this:

process_times:
----------------------------------------------------------------
machine_id | load_id | start_time          | end_time
----------------------------------------------------------------
220        | 25      | 06/24/2012 04:29:00 | 06/25/2012 04:42:38
187        | 23      | 06/22/2012 14:41:00 | 06/24/2012 00:34:32
187        | 18      | 06/20/2012 11:57:00 | 06/20/2012 23:53:51

I’m trying to write a query that will return a relation with an attribute representing the down time between loads of each machine. By down time I mean the time in between each end_time and the following start_time for a given machine.

So for the above example I’d get a result like:

result:
----------------------
machine_id | down_time
----------------------
220        |  0
187        |  (06/22/2012 14:41:00 - 06/20/2012 23:53:51) -- the actual result, I wrote it like this to be more clear

I’ve been tinkering with this for a good chunk of the afternoon and it’s only a pre requisite to the query I’m really trying to write so I figured I would post to see if anyone had any pointers to get me heading in the right direction.

Edit Another constraint that I should mention is that I need to have the result list the individual down times for each machine and not just the total amount of down time over a given period of time.

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    Interesting question. You need to start by getting the prev/next record and then doing the subtraction. Fortunately, Oracle has the lead/lag functions for this.

    So:

    select machine_id, (lastend - start_time) as down_time
from (select pt.*,
             lag(end_time, 1) over (partition by machine_id order by end_time) as lastend
      from process_time pt
     ) pt
where lastend is not null

    This finds the previous record with and end time and then calculates the downtime.

    • 0