Dianna Harter <dhar...@mynewplace.com> wrote: > Having trouble getting a window function to sort correctly.
> Given this data > consumer_id | move_date | history_timestamp > -------------+------------+---------------------------- > 12345| 2008-01-05 | 2007-12-11 06:02:26.842171 > 12345| 2008-02-29 | 2008-02-05 07:22:38.04067 > 12345| 2008-02-29 | 2008-07-11 09:03:42.44044 > 23456| 2009-01-01 | 2008-11-12 07:33:32.656658 <-- > 23456| 2009-01-28 | 2008-11-14 01:57:40.264335 > 23456| 2009-01-01 | 2008-12-04 17:14:20.279999 <-- > 23456| 2009-01-01 | 2008-12-31 00:33:37.204968 > 23456| 2009-01-01 | 2011-06-08 04:16:41.646521 > 34567| 2010-05-07 | 2010-06-08 05:14:43.842172 > I'm trying to get the timestamp when the consumer last changed their > move_date. (Notice consumer_id 23456 set their move_date to 2009-01-01 then > changed and then changed it back. In the end, I want the timestamp from when > they changed it to 2009-01-01 the second time.) > My thought was to do an intermediary step to find the timestamp for each time > it switched. From there I can grab the max(timestamp) for each consumer. > [...] > Any suggestions to get the order by to occur first then the partition by or > maybe there another approach that I could use? If I understand the question correctly, try: | SELECT DISTINCT ON (consumer_id) consumer_id, move_date, history_timestamp | FROM (SELECT consumer_id, move_date, history_timestamp, | LAG(move_date) OVER (PARTITION BY consumer_id ORDER BY consumer_id, history_timestamp) AS previous_move_date | FROM consumer_hist) AS SubQuery | WHERE move_date IS DISTINCT FROM previous_move_date | ORDER BY consumer_id, history_timestamp DESC; Tim -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
