時間範圍聚合

Question

我有一個數據集，其中包含日期{yyyy/mm/dd}和時間{h，m，s}和溫度{float}作爲單個列。

我想通過平均函數來彙總每一天的溫度值。

的問題是，我不知道我怎麼可以查詢的時間屬性，例如總{h,m, (0-5)s}和{h,m, (5-10)s}和{h,m, (10-15)s}和...，自動說。

Answer 1

select 
    day, 
    to_char(date_trunc('minute', "time"), 'HH24:MI') as "minute", 
    extract(second from "time")::integer/5 as "range", 
    avg(temperature) as average 
from (
    select d::date as day, d::time as "time", random() * 100 as temperature 
    from generate_series('2012-01-01', '2012-01-03', '1 second'::interval) s(d) 
) d 
group by 1, 2, 3 
order by 1, 2, 3 
; 

如果你想爲所有天數的平均：

select 
    to_char(date_trunc('minute', "time"), 'HH24:MI') as "minute", 
    extract(second from "time")::integer/5 as "range", 
    avg(temperature) as average 
from (
    select d::time as "time", random() * 100 as temperature 
    from generate_series('2012-01-01', '2012-01-03', '1 second'::interval) s(d) 
) d 
group by 1, 2 
order by 1, 2 
; 

我覺得你的問題的重要組成部分，是一羣以秒的範圍大小劃分的整數結果。