Question

所以我被告知循环在SQL中不是一件理想的事情。以下问题根据年龄范围制作直方图。如您所见，所有组都是硬编码的。在这种情况下，我正在寻找的所有值都在100以下。如果这些值达到数千个，该怎么办？如何才能使其更具可扩展性？

select bins, count(*) as numbers from
(

select id, patientage,
case 
    when patientage between 20 and 29 then '20-29' 
    when patientage between 30 and 39 then '30-39'
    when patientage between 40 and 49 then '40-49'
    when patientage between 50 and 59 then '50-59'
    when patientage between 60 and 69 then '60-69'
    when patientage between 70 and 79 then '70-79'
    when patientage between 80 and 89 then '80-89'
    when patientage between 90 and 99 then '90-99'


end as bins
from patient
inner join tblhospitals on tblhospitals.hospitalnpi=patient.hospitalnpi
where (tblhospitals.hospitalname like '%university%')
) as t
group by bins
order by bins

Answer 1

这是一个稍微通用的形式，可以替换为其他值：

select
    cast(
        patientage / cast(bucketsize as int)
            * cast(bucketsize as int) as varchar(10)) + '-' +
    cast(
        patientage / cast(bucketsize as int)
            * cast(bucketsize as int) + cast(bucketsize as int) - 1 as varchar(10))
...

Answer 2

而不是您的case语句，您可以改为按patientage / 10分组。例如，如果您将查询重写为：

SELECT bins, COUNT(*) AS numbers
FROM (
    SELECT id, patientage, patientage / 10 AS bins
    FROM patient P
        INNER JOIN tblhospitals H ON H.hospitalnpi = P.hospitalnpi
    WHERE H.hospitalname LIKE '%university%'
) AS T
GROUP BY bins
ORDER BY bins

您将获得相同的数据，除了代替'50 -59'，您将得到5，这实际上只是一个可以在SQL之外处理的显示问题。（或者，如果你真的必须，你可以做一些数据按摩用于显示目的，如铸造箱* 10和箱* 10 + 9到varchar等）

Answer 3

有人可能会稍微清理一下，但想法是

select CAST(patientage/ 10 * 10 as varchar) + ' - ' + CAST((patientage/ 10 * 10) + 9 as varchar) as bins

声明和循环时的情况？

3 个答案: