> On 26 Mar 2015, at 1:25, Lavrenz, Steven M <slavrenz@xxxxxxxxxx> wrote: > > 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 > > > > 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. 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 > > > > 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 > > > > 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! Easiest would be to insert the missing values in your table, something like: WITH RECURSIVE calendar (missing_date) AS ( SELECT MAX(check_in_date) FROM table_a WHERE comm_failure = 'YES' UNION ALL SELECT missing_date + interval '1 day' FROM calendar WHERE missing_date < CURRENT_DATE ) INSERT INTO table_a (object_id, channel, check_in_date, comm_failure) SELECT b.object_id, b.channel. c.missing_date, 'YES' FROM table_b b, calendar c WHERE NOT EXISTS ( SELECT 1 FROM table_a a WHERE a.object_id = b.object_id AND a.channel = b.channel AND a.check_in_date = c.missing_date ); That's off the top of my head, untested, etc, but I think I got that mostly right. Alban Hertroys -- If you can't see the forest for the trees, cut the trees and you'll find there is no forest. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
