Question

考虑下表，我如何将这些分数分组为三个桶（不多于）：小于等于150，在150到350之间，超过350。

 id | score
----+-------
  1 |     5
  2 |     5
  3 |     5
  4 |     4
  5 |     5
  6 |     4
  7 |     4
  8 |     4
  9 |     2
 10 |     2
 11 |     6
 12 |   205
 13 |   250
 13 |   400
 14 |   105
 15 |   900
 16 |   1300

我试过这个方法：

select (score/100)*100 || '-' || (score/100)*100 + 100 as scorerange,count(*)
from scores group by score/100 order by score/100;

这就是结果：

 scorerange | count
------------+-------
 0-100      |    11
 100-200    |     1
 200-300    |     2
 400-500    |     1
 900-1000   |     1
 1300-1400  |     1
(6 rows)

它将分数分组，但不在我需要的三个分组中。

Answer 1

这将为您提供所需的范围：

SELECT 
    CASE WHEN min(score) <= 150 THEN '*-150'
         WHEN min(score) <= 350 THEN '151-350'
         ELSE '350-*'
         END AS scorerange, #A comma is needed here right after scorerange
    count(*)
FROM scores
GROUP BY score <= 150, score <= 350;

Answer 2

此查询将为您提供预期的输出。

SELECT CASE WHEN Score <= 150 THEN '0-150'
         WHEN Score >= 350 THEN '150-350'
         ELSE '350+' END AS SCORE_RANGE,             
         COUNT(*) AS COUNT
    FROM SCORES
    GROUP BY SCORE_RANGE

将记录分组到Postgres中的三个预定义桶中

2 个答案: