Alright everyone, this is a doozy of a problem. I am new to Postgres so I appreciate patience/understanding. I have a database of hardware objects, each of which has several different "channels". Once per day, these channels are supposed to check in with a central server, generating an event log table (TABLE A) like the following:
object_id channel check-in date
****************************************
990 1 2014-12-01
990 1 2014-12-02
990 2 2014-12-01
990 2 2014-12-02
286 2 2014-12-01
286 2 2014-12-02
286 5 2014-12-01
286 5 2014-12-02
4507 1 2014-12-01
4507 1 2014-12-02
4507 2 2014-12-01
4507 2 2014-12-02
And so on. Occasionally, communications will break down to the hardware, such
that no reporting occurs. For example, let's say that object 286 loses
communications on 12/1/2014. Then the table might look like:
object_id channel check-in date
****************************************
990 1 2014-12-01
990 1 2014-12-02
990 2 2014-12-01
990 2 2014-12-02
286 2 2014-12-02
286 5 2014-12-02
4507 1 2014-12-01
4507 1 2014-12-02
4507 2 2014-12-01
4507 2 2014-12-02
Or let's say that for some reason, just channel 2 loses reporting for a day.
Then we would have:
object_id channel check-in date
****************************************
990 1 2014-12-01
990 1 2014-12-02
990 2 2014-12-01
990 2 2014-12-02
286 2 2014-12-02
286 5 2014-12-01
286 5 2014-12-02
4507 1 2014-12-01
4507 1 2014-12-02
4507 2 2014-12-01
4507 2 2014-12-02
I have a second table (TABLE B) with all of the object_ids and channels that
are supposed to be reporting in each day. For cases where a certain channel
does not check in, I want to add a column that indicates the comm failure. So,
for the example where all channels on object 286 do not check in, I would like
to get is something like this:
object_id channel check-in date
comm failure
**********************************************************
990 1 2014-12-01
No
990 1 2014-12-02
No
990 2 2014-12-01
No
990 2 2014-12-02
No
286 2 2014-12-01
Yes
286 2 2014-12-02
No
286 5 2014-12-01
Yes
286 5 2014-12-02
No
4507 1 2014-12-01
No
4507 1 2014-12-02
No
4507 2 2014-12-01
No
4507 2 2014-12-02
No
I have been racking my mind for the better part of a day on how to do this. The
thing is that I can do a right join of TABLE B on TABLE A, and this will
populate the missing object ids and channels. However, this only works for a
single day, and it gives me something like:
object_id channel check-in date
comm failure
**********************************************************
990 1 2014-12-01
No
990 1 2014-12-02
No
990 2 2014-12-01
No
990 2 2014-12-02
No
286 2
Yes
286 2 2014-12-02
No
286 5
Yes
286 5 2014-12-02
No
4507 1 2014-12-01
No
4507 1 2014-12-02
No
4507 2 2014-12-01
No
4507 2 2014-12-02
No
I need to do a count of comm failures by day, so I need to populate the
check-in date field. Please help!
Best Regards,
Steve
*************************************************
Steven Lavrenz, MS, EIT
Doctoral Research Fellow, Ph.D. Candidate
Purdue University | Transportation Engineering
Hampton Hall of Civil Engineering, Room 1122
550 Stadium Mall Drive
West Lafayette, IN 47907
765-775-6423
slavr...@purdue.edu<https://exchange.purdue.edu/owa/redir.aspx?C=1KvRJRKXRUmCQXrzhc8xxDD2sumyJNIICxsOWx4t9faOapFqc_-gBVMV21AYScHluQX0uMJmOYA.&URL=mailto%3aslavrenz%40purdue.edu>
