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

我在这里看到的答案在SQL Server的语法中行不通。我会用:

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'
    when score between 20 and 29 then '20-29'
    ...
    else '90-99' end as range
  from scores) t
group by t.range

编辑:见评论

其他回答

另一种方法是将范围存储在表中,而不是将它们嵌入到查询中。你最终会得到一个表,命名为Ranges,它看起来像这样:

LowerLimit   UpperLimit   Range 
0              9          '0-9'
10            19          '10-19'
20            29          '20-29'
30            39          '30-39'

查询如下所示:

Select
   Range as [Score Range],
   Count(*) as [Number of Occurences]
from
   Ranges r inner join Scores s on s.Score between r.LowerLimit and r.UpperLimit
group by Range

这确实意味着要建立一个表,但是当所需的范围发生变化时,维护这个表是很容易的。不需要更改代码!

select cast(score/10 as varchar) + '-' + cast(score/10+9 as varchar), 
       count(*)
from scores
group by score/10

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!

我在这里看到的答案在SQL Server的语法中行不通。我会用:

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'
    when score between 20 and 29 then '20-29'
    ...
    else '90-99' end as range
  from scores) t
group by t.range

编辑:见评论

declare @RangeWidth int

set @RangeWidth = 10

select
   Floor(Score/@RangeWidth) as LowerBound,
   Floor(Score/@RangeWidth)+@RangeWidth as UpperBound,
   Count(*)
From
   ScoreTable
group by
   Floor(Score/@RangeWidth)