thx for the help! this did it then for an individual collection and its fast :-):
SELECT OneM.f_timestamp, FiveM.f_ds, FiveM.f_us, OneM.f_ds, OneM.f_us FROM td_fetch1m_by_rrd_id OneM left join (select f_rrd_id, f_ds, f_us, f_timestamp from td_fetch_by_rrd_id where f_rrd_id = 444) FiveM ON (OneM.f_timestamp = FiveM.f_timestamp) where OneM.f_rrd_id = 444 ORDER BY OneM.f_timestamp; ________________________________ From: Justin <jus...@emproshunts.com> To: Kashmir <kashmir_us_1...@yahoo.com> Cc: pgsql-sql@postgresql.org Sent: Wednesday, April 8, 2009 9:38:22 PM Subject: Re: [SQL] join help Kashmir wrote:only difference is: first table stores data per 'f_rrd_id' evey 5min, and the second table every single minute. I want to run a query that would return for the same 'f_rrd_id' all values from both tables sorted by f_timestamp, of course a set would only have values from the 5m table if the timestamp was present there too (every 5th set only) being a sql-lamer, i used some query builder help to build my query (which served me quite well in the past for all my 'complicated' sqls), and was suggested for f_rrd_id=444 to use something as: SELECT td_fetch1m_by_rrd_id.f_timestamp, td_fetch_by_rrd_id.f_ds, td_fetch_by_rrd_id.f_ds, td_fetch1m_by_rrd_id.f_ds, td_fetch1m_by_rrd_id.f_us FROM td_fetch_by_rrd_id RIGHT JOIN td_fetch1m_by_rrd_id ON td_fetch_by_rrd_id.f_timestamp=td_fetch1m_by_rrd_id.f_timestamp WHERE td_fetch1m_by_rrd_id.f_rrd_id=444 ORDER BY td_fetch1m_by_rrd_id.f_timestamp; and this works quite fine and as expected in the source env (some gui-sqler). but when i take this into psql, i get totally messed up results, the values just dont make any sense... The sql is joining on a time stamp?? Using the time stamp i would expect odd ball results because a several unique f_rr_id could have the same timestamp especially if its heavy write table . every 5th set only ???? What does this mean what makes something the 5th set. I normally avoid table aliasing but these names i'm having a real tough time reading so we are going to use 1Minute = td_fetch1m_by_rrd_id and the 5Minute = td_fetch_by_rrd_id from here on out. You want to join whats in the 1Minute table to whats in the 5Minute only if it is in the 5Minute table and only return from 1Minute table where the timestamps is in the 5Minute table If my understanding is correct this will work minus any typos. To create a join condition we need a composite identity to join on. So what i did is cast F_rr_id and F_timestamp to text adding them together to create a unique condition to join on. Also there is a typo above noted in bold f_ds is listed twice i believe that is a mistake. SELECT OneM.f_timestamp, FiveM.f_ds, FiveM.f_us, OneM.f_ds, OneM.f_us FROM td_fetch1m_by_rrd_id OneM, left Join (select f_rrd_id, f_ds, f_us, f_timestamp from td_fetch_by_rrd_id ) FiveM ON (OneM.f_rrd_id::text || OneM.f_timestamp::text) = (FiveM.f_rrd_id::text || FiveM.f_timestamp::text) ORDER BY OneM.f_timestamp;