Finding any rows where the latest event time is over a specified period
The relates to OpenNMS where I'm trying to write an automation in SQL. I have a system which sends events to a table every time the backup succeeds. I want to detect if the backup is overdue for any given node. So for example the (simplified) table looks like:

    nodeid, eventid, eventuei, eventtime
      1   ,  1     , backupOk, 09:20 15/12/09
      2   ,  2     , backupOk, 09:25 15/12/09
      3   ,  3     , backupOk, 09:30 15/12/09
      1   ,  4     , backupOk, 09:20 16/12/09
      2   ,  5     , backupOk, 09:25 16/12/09
      2   ,  6     , backupOk, 09:25 17/12/09
      3   ,  7     , backupOk, 09:30 17/12/09

So what I need is a list of nodeid's where the backup is overdue by 24 hours (and I guess where no backup has occurred at all, although there are nodes in this database that don't get backed up (as they are different types of node)).


Finding any rows where the latest event time is over a specified period
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The relates to OpenNMS where I'm trying to write an automation in SQL. I have a system which sends events to a table every time the backup succeeds. I want to detect if the backup is overdue for any given node. So for example the (simplified) table looks like:

    nodeid, eventid, eventuei, eventtime
      1   ,  1     , backupOk, 09:20 15/12/09
      2   ,  2     , backupOk, 09:25 15/12/09
      3   ,  3     , backupOk, 09:30 15/12/09
      1   ,  4     , backupOk, 09:20 16/12/09
      2   ,  5     , backupOk, 09:25 16/12/09
      2   ,  6     , backupOk, 09:25 17/12/09
      3   ,  7     , backupOk, 09:30 17/12/09

So what I need is a list of nodeid's where the backup is overdue by 24 hours (and I guess where no backup has occurred at all, although there are nodes in this database that don't get backed up (as they are different types of node)).

