postgresql - 按时间范围聚合

Question

我有一个数据集，其中包含日期 {yyyy/mm/dd} 和时间 {h,m,s} 以及温度 {float} 作为单独的列。

我想通过平均函数汇总每一天的温度值。

问题是，我不知道如何查询时间属性来表示聚合 {h,m, (0-5)s} 和 {h ,m, (5-10)s} 和 {h,m, (10-15)s} 和...，自动。

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
;

如果你想要所有天的平均值:

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
;

我认为您的问题的重要部分是按秒除以范围大小的整数结果进行分组。