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

我会用一种稍微不同的方式来做,这样它就不必定义每种情况:

select t.range as [score range], count(*) as [number of occurences]
from (
  select FLOOR(score/10) as range
  from scores) t
group by t.range

没有测试过,但你懂的…

其他回答

create table scores (
   user_id int,
   score int
)

select t.range as [score range], count(*) as [number of occurences]
from (
      select user_id,
         case when score >= 0 and score < 10 then '0-9'
         case when score >= 10 and score < 20 then '10-19'
         ...
         else '90-99' as range
     from scores) t
group by t.range

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

在我看来,James Curran的回答是最简洁的,但输出并不正确。对于SQL Server,最简单的语句如下:

SELECT 
    [score range] = CAST((Score/10)*10 AS VARCHAR) + ' - ' + CAST((Score/10)*10+9 AS VARCHAR), 
    [number of occurrences] = COUNT(*)
FROM #Scores
GROUP BY Score/10
ORDER BY Score/10

这假设了一个我用来测试它的#Scores临时表,我只是用0到99之间的随机数填充了100行。

select t.blah 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 blah
  from scores) t
group by t.blah

如果在MySQL中,请确保使用'range'以外的单词,否则在运行上述示例时会出现错误。

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!