On Sat, Oct 20, 2012 at 8:02 AM, Raymond O'Donnell <rod@xxxxxx> wrote: > On 20/10/2012 11:54, ochaussavoine wrote: >> Hi, >> I have a table 'tmvt' with a field 'created' in the row, and would like to >> compute the difference between successive rows. The solution I found is: >> > > I think you can do it with a window function. > > http://www.postgresql.org/docs/9.2/static/tutorial-window.html > http://www.postgresql.org/docs/9.2/static/functions-window.html > > Ray. In particular you're looking probably for the lag() window function. For example if you have a timestamp column "ts" that's increasing monotonically and you want to check the difference of each row's timestamp with the chronologically previous row's timestamp you'd do something like: $ SELECT id, ts, lag(ts) OVER (order by ts) AS prev_ts FROM mytable; This will display as third column the previous row's ts. You may find reading this introduction to window fuctions useful: https://www.pgcon.org/2009/schedule/attachments/98_Windowing%20Functions.pdf best tregards, Thalis -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
