David Johnston wrote > Basic idea: use ORDER BY in the window to auto-define a range-preceding > frame. Create an array of all dates (tags in the example) that match with > positive amounts. Negative amounts get their matching tag added to the > array as NULL. The provided function looks into the generated array and > returns the last (closest to the current row in the frame) non-null > date/tag in the array which ends up being the date/tag matching the last > positive amount in the frame. > > David J.
Hi David, Thanks for your reply. This is an approach I also considered, but hoped for a solution without the expense (albeit small) of having to create a function. Just wanted to confirm that I'm not missing a simpler solution (my knowledge in terms of window functions is rather limited). Until something better comes along, I'll implement the solution as suggested here. Regards GMB -- View this message in context: http://postgresql.1045698.n5.nabble.com/Help-needed-with-Window-function-tp5773160p5773196.html Sent from the PostgreSQL - sql mailing list archive at Nabble.com. -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
