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?
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
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。
其他回答
在SQL Server 2000上,投票最多的答案都不正确。也许他们用的是另一个版本。
下面是在SQL Server 2000上这两个软件的正确版本。
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
or
select t.range as [score range], count(*) as [number of occurrences]
from (
select user_id,
case when score >= 0 and score< 10 then '0-9'
when score >= 10 and score< 20 then '10-19'
else '20-99' 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!
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;
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!
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