Postgresql Percentile_Cont 不工作：函数 percentile_cont（数字，字符变化，数字）不存在

Question

我有一个 table TableX 看起来像：

Name	Value
Bob	100
Cathy	500
Cathy	200
Cathy	100

我想处理值列的中位数以获得：

Name	Value
Bob	100
Cathy	200

我正在尝试使用 percentile_cont:

select name, percentile_cont(0.5) within group (order by name, value) from TableX

但是获取错误：

ERROR:  function percentile_cont(numeric, character varying, numeric) does not exist

我的 postgresql 版本是 13+，下面一行确实有效。

SELECT percentile_cont(array(SELECT j/10.0 FROM generate_series(1,10) j)) WITHIN GROUP(ORDER BY i) AS median FROM generate_series(1,11) AS s(i);

很确定我的脚本是错误的...非常感谢您的想法。谢谢！

Answer 1

create table percent_test (name varchar, value float);

insert into percent_test values ('Bob', 100), ('Cathy', 500), ('Cathy', 200), ('Cathy', 100);

select name, percentile_cont(0.5) within group (order by value) from  percent_test group  by name;
 name  | percentile_cont 
-------+-----------------
 Bob   |             100
 Cathy |             200

根据 Aggregate Functions:

percentile_cont ( fraction double precision ) WITHIN GROUP ( ORDER BY double precision ) → double precision

percentile_cont ( fraction double precision ) WITHIN GROUP ( ORDER BY interval ) → interval

Computes the continuous percentile, a value corresponding to the specified fraction within the ordered set of aggregated argument values. This will interpolate between adjacent input items if needed.

所以within group中的order by只能是数值，不能是字符值。将 name 分组推送到查询的 from 部分。

Postgresql Percentile_Cont 不工作：函数 percentile_cont（数字，字符变化，数字）不存在

Postgresql Percentile_Cont not working: function percentile_cont(numeric, character varying, numeric) does not exist

postgresql

median