Panos Kassianidis wrote:
> and I would like to retrieve values recorded in the last 2 hours but
> with an interval of 5 minutes, which means that my query should return
> one tuple for every 5 tuples in the table and the value of this tuple
> should be an average of 5 values.
> Does anyone have any clue how I can make this query? I have though
> about somehow grouping the tuples with group by and use the AVG
> function but the tuples don't have anything in common to be grouped by.
You'll need to write an enhanced version of date_trunc() that can group
timestamps into arbitrary units, e.g. my_date_trunc('... 12:34', 'm', 5) = '...12:30'
Then you can group by your new value.
-- Richard Huxton Archonet Ltd