SQL order by ASC Second(value) space ASC First(value) 在聚合 SQL 查询的同一列中

Posted 2023-03-29

【中文标题】SQL order by ASC Second(value) space ASC First(value) 在聚合 SQL 查询的同一列中

【英文标题】：SQL order by ASC Second(value) space ASC First(value) in same column in aggregate SQL query

【发布时间】：2022-01-01 16:36:47

【问题描述】：

我想按列名称排序，该列名称在同一列中具有 "Value1" Space "Value2" 之类的值。 例如。

Column1
Value1 value2
NSPP02 2111
NSPP02 2110
NSPP01 2111

我想先按 value2 排序，然后按 value1 排序。 ASC 按值 2，然后按值 1 ASC。

我使用聚合如下：

select 
    pdc.semester as Semester,
    count(pdc.CNIC) as TotalRegistrations,
    count(s.studentid) as TotalRegistered,
    count(case when r.Grade is not null then 'Appeared' end) as Appeared,
    count(case when r.Grade='f' then 'fail' end) as Failed,
    count(case when r.grade <>'f' then 'pass' end) as Passed
from
    PDC_PreRegistration pdc 
left join  
    Students s on pdc.Semester = s.CurSemester and s.nic = pdc.CNIC
left join 
    studentresultnet r on s.studentid = r.studentid and s.CurSemester = r.Semester 
left join 
    semester se on se.Semester = r.Semester
where 
    pdc.semester in (select CurSemester from students where batch = 'PD2110') 
group by 
    pdc.Semester
order by  
    semester desc

本次查询的结果如下：

Semester	TotalRegistrations	TotalRegistered	Appeared	Failed	Passed
NSPP02 2111	121	81	0	0	0
NSPP02 2110	37	35	24	1	23
NSPP01 2111	76	42	0	0	0

我希望结果是这样的：

Semester	TotalRegistrations	TotalRegistered	Appeared	Failed	Passed
NSPP02 2110	37	35	24	1	23
NSPP01 2111	76	42	0	0	0
NSPP02 2111	121	81	0	0	0

按值 2 进行 ASC，然后按值 1 进行 ASC。

学期列的示例序列如下：

NSPP01 2110 NSPP02 2110 NSPP01 2111 NSPP02 2111 NSPP01 2112 NSPP02 2112 NSPP01 2201 NSPP02 2201 NSPP01 2202 NSPP02 2202 NSPP01 2203 NSPP02 2203

等等

查看此屏幕截图：

Screenshot of query and its result

【问题讨论】：

如果您对单独的部分感兴趣，将两个值存储在一列中是个坏主意。相应地改变你的桌子设计，你已经解决了这个问题。

【参考方案1】：

我不确定您的原因或该列背后的逻辑，但理想情况下，您应该将它们作为 2 个单独的列。它使这样的事情变得更容易。

话虽如此，我认为有两种方法可以解决这个问题。

如果您的 2 个值的长度永远不会改变，即值 NSPP02 将始终包含 5 个字符，而 2203 值将始终包含 4 个字符，那么您可以执行以下操作：

SELECT LEFT(COLUMN_1,5) AS VALUE 1
SELECT RIGHT(COLUMN_1,4) AS VALUE 2
ORDER BY VALUE 2, VALUE 1

或者，如果每个值中的字符数有增加的空间，那么您将需要使用类似 SUBSTRING 函数的东西。有一些不错的细节here：

【参考方案2】：

您实际上可以先拆分学期列和SORT，然后您可以抑制这些辅助列以获得所需的输出：

SELECT Semester, TotalRegistrations, TotalRegistered, Appeared, Failed, Passed
FROM(
SELECT pdc.semester as Semester,count(pdc.CNIC) as 
       TotalRegistrations,count(s.studentid) as TotalRegistered,
       count(case when r.Grade is not null then 'Appeared' end) as Appeared,
       count(case when r.Grade='f' then 'fail' end) as Failed,
       count(case when r.grade <>'f' then 'pass' end) as Passed,
       TRIM(LEFT(pdc.semester, CHARINDEX(' ', pdc.semester) - 1)) as frst, 
       TRIM(RIGHT(pdc.semester, LEN(pdc.semester) - CHARINDEX(' ', pdc.semester))) as sec
FROM PDC_PreRegistration pdc 
LEFT JOIN Students s on pdc.Semester=s.CurSemester and s.nic=pdc.CNIC
LEFT JOIN studentresultnet r on s.studentid=r.studentid and s.CurSemester=r.Semester 
LEFT JOIN semester se on se.Semester=r.Semester
WHERE pdc.semester
IN (select CurSemester from students where  batch='PD2110')
GROUP BY pdc.Semester
)
ORDER BY sec, frst