假设我有一个带有数字列的表(让我们称之为“score”)。

我想生成一个计数表,显示分数在每个范围内出现的次数。

例如:

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

在这个示例中,有11行分数在0到9之间,14行分数在10到19之间,3行分数在20到29之间。

有什么简单的方法吗?你有什么建议吗?


当前回答

也许你问的是如何让这样的事情继续下去……

当然,您将为查询调用全表扫描,如果包含需要统计(聚合)的分数的表很大,您可能想要一个性能更好的解决方案,您可以创建一个辅助表并使用规则,例如关于插入—您可能会研究它。

不过,并不是所有的RDBMS引擎都有规则!

其他回答

Try

SELECT (str(range) + "-" + str(range + 9) ) AS [Score range], COUNT(score) AS [number of occurances]
FROM (SELECT  score,  int(score / 10 ) * 10  AS range  FROM scoredata )  
GROUP BY range;

因为要排序的列(Range)是一个字符串,所以使用字符串/单词排序而不是数值排序。

只要字符串有0来填充数字长度,排序在语义上仍然是正确的:

SELECT t.range AS ScoreRange,
       COUNT(*) AS NumberOfOccurrences
  FROM (SELECT CASE
                    WHEN score BETWEEN 0 AND 9 THEN '00-09'
                    WHEN score BETWEEN 10 AND 19 THEN '10-19'
                    ELSE '20-99'
               END AS Range
          FROM Scores) t
 GROUP BY t.Range

如果范围是混合的,简单地填充一个额外的0:

SELECT t.range AS ScoreRange,
       COUNT(*) AS NumberOfOccurrences
  FROM (SELECT CASE
                    WHEN score BETWEEN 0 AND 9 THEN '000-009'
                    WHEN score BETWEEN 10 AND 19 THEN '010-019'
                    WHEN score BETWEEN 20 AND 99 THEN '020-099'
                    ELSE '100-999'
               END AS Range
          FROM Scores) t
 GROUP BY t.Range

也许你问的是如何让这样的事情继续下去……

当然,您将为查询调用全表扫描,如果包含需要统计(聚合)的分数的表很大,您可能想要一个性能更好的解决方案,您可以创建一个辅助表并使用规则,例如关于插入—您可能会研究它。

不过,并不是所有的RDBMS引擎都有规则!

在postgres中(其中||是字符串连接操作符):

select (score/10)*10 || '-' || (score/10)*10+9 as scorerange, count(*)
from scores
group by score/10
order by 1

给:

 scorerange | count 
------------+-------
 0-9        |    11
 10-19      |    14
 20-29      |     3
 30-39      |     2

下面是如何在T-SQL中做到这一点:

DECLARE @traunch INT = 1000;

SELECT 
    CONCAT
    ( 
      FORMAT((score / @traunch) * @traunch, '###,000,000') 
      , ' - ' , 
      FORMAT((score / @traunch) * @traunch + @traunch - 1, '###,000,000') 
    ) as [Range]
  , FORMAT(MIN(score), 'N0') as [Min]
  , FORMAT(AVG(score), 'N0') as [Avg]
  , FORMAT(MAX(score), 'N0') as [Max]
  , FORMAT(COUNT(score), 'N0') as [Count]
  , FORMAT(SUM(score), 'N0') as [Sum]
FROM scores
GROUP BY score / @traunch
ORDER BY score / @traunch

select t.range as score, count(*) as Count 
from (
      select UserId,
         case when isnull(score ,0) >= 0 and isnull(score ,0)< 5 then '0-5'
                when isnull(score ,0) >= 5 and isnull(score ,0)< 10 then '5-10'
                when isnull(score ,0) >= 10 and isnull(score ,0)< 15 then '10-15'
                when isnull(score ,0) >= 15 and isnull(score ,0)< 20 then '15-20'               
         else ' 20+' end as range
         ,case when isnull(score ,0) >= 0 and isnull(score ,0)< 5 then 1
                when isnull(score ,0) >= 5 and isnull(score ,0)< 10 then 2
                when isnull(score ,0) >= 10 and isnull(score ,0)< 15 then 3
                when isnull(score ,0) >= 15 and isnull(score ,0)< 20 then 4             
         else 5  end as pd
     from score table
     ) t

group by t.range,pd order by pd