标签: percentile-cont

我需要从一些数据生成特定的报告，并且在弄清楚 PERCENTILE_CONT 的正确用法以提供我需要的结果时遇到了很大的麻烦。我想在查询结果中包含一列，该列显示一系列值中第 95 个百分位的值。

我有一个表如下：

customer_id sale_amount sale_date
1   265.75  2019-09-11 00:00:04.000
1   45.75   2019-09-10 01:00:04.000
1   2124.77 2019-09-10 04:00:04.000
1   66.99   2019-09-10 04:20:04.000
1   266.49  2019-09-09 11:20:04.000
1   3266.49 2019-09-08 11:20:04.000

非常简单。

我可以运行以下查询，没有问题：

select
    min(sale_amount) as minimum_sale,
    max(sale_amount) as maximum_sale,
    avg(sale_amount) as average_sale
from
    sales
where
    customer_id = 1;

这会产生以下输出：

minimum_sale    maximum_sale    average_sale
45.75           3266.49     1006.040000

我想要的是第四列 perc_95，它将计算代表 sale_amount 的第 95 个百分位数的值。

这可以让我获得价值：

select distinct
    customer_id,
    percentile_cont(0.95) WITHIN GROUP (order by sale_amount) OVER (partition by customer_id) as perc_95 …

我目前有一个查询，其工作方式如下：

select AVG(t2 - t1) as delay,
       percentile_cont(0.25) within group (order by (t2 - t1)) as q25,
       percentile_cont(0.5) within group (order by (t2 - t1)) as median,
       percentile_cont(0.75) within group (order by (t2 - t1)) as q75,
       p.bool1,
       p.cat1
from people p
group by p.bool1, p.cat1
order by p.cat1,p.bool1

但是，我在 postgres 函数聚合页面上阅读： https://www.postgresql.org/docs/9.4/functions-aggregate.html

我应该能够指定多个分位数：

percentile_cont(fractions) WITHIN GROUP (ORDER BY sort_expression)  double precision[]  double precision or interval    array of sort expression's type     multiple continuous percentile: returns an array of results matching …