如何在单个 Teradata 查询中输出不同的第 25、50、75 个百分位数？

Question

几个小时前，我在类似的事情上陷入困境，并制定了一个不太混乱的代码，用于在单个 Teradata 查询中输出第 25、50、75 个百分位数。可以进一步扩展以生成“5 点摘要”。根据您的人口估计，对于最小和最大变化静态值。

某处有人要求一种优雅的方法。分享我的。

代码如下：

SELECT MAX(PER_MIN) AS PER_MIN,
       MAX(PER_25) AS PER_25,
       MAX(PER_50)  AS PER_50,
       MAX(PER_75)  AS PER_75,
       MAX(PER_MAX) AS PER_MAX
FROM (SELECT CASE WHEN ROW_NUMBER() OVER(ORDER BY DURATION_MACRO_CURR ASC) = CAST(COUNT(*) OVER() * 0.01 AS INT) THEN DURATION_MACRO_CURR END AS PER_MIN,
             CASE WHEN ROW_NUMBER() OVER(ORDER BY DURATION_MACRO_CURR ASC) = CAST(COUNT(*) OVER() * 0.25 AS INT) THEN DURATION_MACRO_CURR END AS PER_25,
             CASE WHEN ROW_NUMBER() OVER(ORDER BY DURATION_MACRO_CURR ASC) = CAST(COUNT(*) OVER() * 0.50 AS INT) THEN DURATION_MACRO_CURR END AS PER_50
             CASE WHEN ROW_NUMBER() OVER(ORDER BY DURATION_MACRO_CURR ASC) = CAST(COUNT(*) OVER() * 0.75 AS INT) THEN DURATION_MACRO_CURR END AS PER_75
             CASE WHEN ROW_NUMBER() OVER(ORDER BY DURATION_MACRO_CURR ASC) = CAST(COUNT(*) OVER() * 0.99 AS INT) THEN DURATION_MACRO_CURR END AS PER_MAX
      FROM PROD_EXP_DL_CVM.PROD_CVM
      WHERE PW_END_DATE =  '2016-10-18'
    ) BASE

这是所需的输出：

Answer 1

我会使用条件聚合来做到这一点：

select min(DURATION_MACRO_CURR) as min_val,
       min(case when seqnum / 0.25 >= cnt then DURATION_MACRO_CURR end) as 25_percentile,
       min(case when seqnum / 0.50 >= cnt then DURATION_MACRO_CURR end) as 50_percentile,
       min(case when seqnum / 0.75 >= cnt then DURATION_MACRO_CURR end) as 75_percentile,
       max(DURATION_MACRO_CURR) as max_val
from (select pc.*,
             row_number() over (order by DURATION_MACRO_CURR) as seqnum,
             count(*) over () as cnt
      from PROD_EXP_DL_CVM.PROD_CVM pc
      where pc.PW_END_DATE =  '2016-10-18'
     ) pc;

如何在单个 Teradata 查询中输出不同的第 25、50、75 个百分位数？

How to output different 25th, 50th, 75th percentiles in single Teradata query?

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