Re: Populating missing dates in postgresql data - Mailing list pgsql-general
| From | David G. Johnston |
|---|---|
| Subject | Re: Populating missing dates in postgresql data |
| Date | |
| Msg-id | CAKFQuwaaw27EoO7M0z5FemJxHD39RGxhbeixZRY5vPKvExFPiQ@mail.gmail.com Whole thread Raw |
| In response to | Populating missing dates in postgresql data ("Lavrenz, Steven M" <slavrenz@purdue.edu>) |
| Responses |
Re: Populating missing dates in postgresql data
|
| List | pgsql-general |
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!
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