Hello see http://okbob.blogspot.com/2009/11/aggregate-function-median-in-postgresql.html Regards Pavel Stehule 2010/11/16 maarten <maarten.foque@xxxxxxxxx>: > Hello everyone, > > I was doing some analysis of data to find average delays between some > timestamp values etc... > When the number of rows the average is computed over is small, this can > give distorted values. ÂSo I've obviously added a count column to see if > the average represents much data. > However, I would also like to add the median value to give me a pretty > good idea of whats happening even for smaller counts. > > I couldn't find such an aggregate function in the manual (version 8.3) > and some websearching didn't uncover it either. > > I was thinking about > SELECT max(id) FROM test ORDER BY id ASC LIMIT > Â Â Â Â(SELECT count(*)/2 FROM test) > > But two things are wrong with that: > Limit can't use subqueries :( > And ORDER BY gives me the error: 'must be used in aggregate function > etc...) but I can probably work around this by using an ordered subquery > in stead of the table directly. > > Furthermore, I need the median for a timestamp column, which would > probably complicate things more than when it is a number column. > > I'd like to be able to do this using only the database. (So no > programming functions, special addons etc...) > > Any ideas anyone? > > regards, > Maarten > > > -- > Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general > -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
