如何在 Postgres 中使用 percentile_conts 和多个分位数

Question

我目前有一个查询是这样工作的：

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 函数聚合页面上看到： 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 the shape of the fractions parameter, with each non-null element replaced by the value corresponding to that percentile

我想使用它，这样我就不会为每个分位数重新计算 t2 - t1。获得多个分位数的正确语法是什么？我需要子查询吗？

Answer 1

I'd like to use this so I don't recalculate the t2 - t1 for every quantile

在这种情况下，横向连接可能会有所帮助：

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

相关：PostgreSQL: using a calculated column in the same query

数组定义为：ARRAY[0.25, 0.5, 0.75]或'{0.25, 0.5, 0.75}'::double precision[]

select AVG(t2 - t1) as delay,
   -- 1
   percentile_cont(ARRAY[0.25, 0.5, 0.75]) within group (order by (t2 - t1)) as q25,
   -- 2
   percentile_cont('{0.25, 0.5, 0.75}'::double precision[]) 
   within group (order by (t2 - t1)) as q
       p.bool1,
       p.cat1
from people p
group by p.bool1, p.cat1
order by p.cat1,p.bool1;

db<>fiddle demo

Is there an easy way to inline specify the names of each of the resulting percentile fields as they had been with q25, q50, q75, etc

WITH cte AS (
    select AVG(t2 - t1) as delay,
       percentile_cont(ARRAY[0.25, 0.5, 0.75]) within group (order by (t2 - t1)) as q,
           p.bool1,
           p.cat1
    from people p
    group by p.bool1, p.cat1
)
select cte.*, q[1] AS q25, q[2] AS q50, q[3] AS q75
from cte
order by cat1,bool1;

db<>fiddle demo2

如何在 Postgres 中使用 percentile_conts 和多个分位数

How to use percentile_conts with multiple quantiles in Postgres

postgresql

quantile

percentile-cont