sql-按范围分组以包括没有值的范围 [英] sql - group by in ranges to include ranges without values

问题描述

假设与这种问题类似的情况 。我想得到以下结果：

Suppose a scenario similar to this question. I want to get the following results:

score range  | number of occurrences
-------------------------------------
   0-9       |        11
  10-19      |        14
  20-29      |         3
   ...       |       ...

然后我可以使用选择的答案作为解决方案：

And I can use the selected answer as a solution:

select t.range as [score range], count(*) as [number of occurences]
from (
  select case  
    when score between 0 and 9 then ' 0- 9'
    when score between 10 and 19 then '10-19'
    else '20-99' end as range
  from scores) t
group by t.range

分组我如何确保分数范围为30即使在该范围内没有结果，也会显示-39？

How can I assure that the score range of 30-39 will be display even when there are no results on that range?

推荐答案

尝试此查询（也在 SQL小提琴）：

WITH ranges AS (
    SELECT (ten*10)::text||'-'||(ten*10+9)::text AS range,
           ten*10 AS r_min, ten*10+9 AS r_max
      FROM generate_series(0,9) AS t(ten))
SELECT r.range, count(s.*)
  FROM ranges r
  LEFT JOIN scores s ON s.score BETWEEN r.r_min AND r.r_max
 GROUP BY r.range
 ORDER BY r.range;

---

编辑：

您可以通过将参数更改为 generate_series（）来轻松调整范围。可以使用以下结构来确保范围始终覆盖您的分数：

You can easily adjust the range by changing parameters to generate_series(). It is possible to use the following construct to make sure ranges will always cover your scores:

SELECT (ten*10)::text||'-'||(ten*10+9)::text AS range,
       ten*10 AS r_min, ten*10+9 AS r_max
  FROM generate_series(0,(SELECT max(score)/10 FROM scores)) AS t(ten))

表示范围 CTE。

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