( sunmao | 2022. 05. 07., szo – 22:09 )

Itt tartok:

select u.hour, MAX(u.val) - MIN(u.val) AS diff
from (
         (select date_trunc('hour', to_timestamp(ts / 1000)) as hour, val::numeric
          from ts_string
          where id = 2
          order by 1, 2 asc)
     ) as u
group by u.hour order by u.hour;

bar nem tudom, hogy ez mennyire elegans...