Are you sur you don't want a moving windows (stddev on 0 to 50 , then stdev on 1 to 51) ..
If you don't want moving windows your query would look like DROP TABLE IF EXISTS your_data; CREATE TABLE your_data AS SELECT s as gid , random() as your_data_value FROM generate_series(1,10000) as s ; SELECT min(gid) as min_gid, max(gid) as max_gid, stddev(your_data_value) as your_stddev FROM your_data GROUP BY (gid-1)/50 ORDER BY min_gid ASC Please note that "min(gid) as min_gid, max(gid) as max_gid" and "ORDER BY min_gid ASC" are just there to help you understand the result Cheers, Rémi-C 2015-01-22 16:49 GMT+01:00 David G Johnston <david.g.johns...@gmail.com>: > Pierre Hsieh wrote > > Hi > > > > This table just has a column which type is integer. There are one million > > data in this table. I wanna calculate standard deviation on each 50 data > > by > > order. It means SD1 is from data 1 to data 50, SD2 is from data 51 to > > 100.... Is there anyone who can give me some suggestions? Thanks > > > > Pierre > > Integer division > > David J. > > > > -- > View this message in context: > http://postgresql.nabble.com/how-to-calculate-standard-deviation-from-a-table-tp5835031p5835042.html > Sent from the PostgreSQL - general mailing list archive at Nabble.com. > > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general >
