Question

如果我有下表stats：

type    duration
------  ---------
get     10
get     15
get     20
put     12
put     14
put     16

我知道我可以通过以下查询获取sum()和average()：

select
    type, 
    sum(duration) as "total duration",
    avg(duration) as "average duration"
from
    stats
group by
    type

我还可以使用窗口函数功能获得90％avg()和max()的持续时间：

select
    type,
    avg("dur") as "average duration of the fastest 90%",
    max("dur") as "max duration of the fastest 90%"
from
(
    select
        type,
        duration as "dur",
        row_number() over (partition by type order by duration asc) as "seqnum"
        count(*) over (partition by type) as "totnum"
    from
        stats
)
where
    "seqnum" <= (.9 * "totnum")
group by
    type

但是我很难理解如何将两者合并在一起，这样我就可以有一个返回的查询：type，total duration，average duration，{{1 }，average duration of the fastest 90%？

Answer 1

使用条件聚合：

select type,
       sum(duration) as "total duration",
       avg(duration) as "average duration",
       avg(case when "seqnum" <= (0.9 * "totnum") then "dur" end) as "average duration of the fastest 90%",
       max(case when "seqnum" <= (0.9 * "totnum") then "dur" end) as "max duration of the fastest 90%"
from (select type, duration as "dur",
             row_number() over (partition by type order by duration asc) as "seqnum",
             count(*) over (partition by type) as "totnum"
      from stats
     ) s
group by type;

Answer 2

你可以试试这个。

select distinct
    type,
    avg("dur") over(partition by type) as "average duration of the fastest 90%",
    max("dur") over(partition by type) as "max duration of the fastest 90%",
    "total duration",
    "average duration"
from
(
    select
        type,
        duration as "dur",
        row_number() over (partition by type order by duration asc) as "seqnum",
        count(*) over (partition by type) as "totnum",
        sum(duration) over(partition by type) as "total duration",
        avg(duration) over(partition by type) as "average duration"
    from
        stats
) x
where 
    "seqnum" <= (.9 * "totnum")

以DB / 2计算总和，平均值和90％

2 个答案: