On Sun, Jul 12, 2009 at 5:53 PM, David Fetter<david@xxxxxxxxxx> wrote: >> [mode would also be useful, as an explicit function, though we can get it >> easily enough using count(1) order by count desc]. > > You can get that with windowing functions, too. :) > >> According to google, this has been a wish since at least year 2000 >> for various people, but doesn't seem to be implemented. > > Patches are welcome :) Trouble in writing such aggregate, would be that it has to keep full set, in order to sort it, and choose n/2 element (in case set contains odd number of elements), or ([n/2]+[(n/2)+1])/2 otherwise. I usually, if in need to calculate it , I usually do it like that (but that's pretty slow on large sets): pg84@atlantic:~$ psql psql (8.4beta2) Type "help" for help. pg84=# create table foo(a int not null); CREATE TABLE pg84=# insert into foo(a) select random()*666 from generate_series(1,666); INSERT 0 666 pg84=# select a from foo order by a limit 1 offset (select count(*)/2 from foo); a ----- 321 (1 row) (yeah, I know it is lame). So , I think in order to create such patch, the aggregate would have to secretly create some temporary table, to store the set first... -- GJ -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
