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嗨，伙计们，我有一张表，用于存储该领域不同科目的学生分数stu_score。主题在 Fieldex_subjects中，我需要查询表格，以便将分数排列为每个主题的单独列。我已经设法查询数学，例如：

select stu_number, stu_name,  ex_name, stu_score as MATHEMATICS 
from EXAMS_MASTER_REGISTER 
where stu_level = '1' and stu_stream = 'EAST' 
and ex_semester = 'FIRST' 
and ex_name = 'MIDYEARS' 
and ex_subject = 'MATHEMATICS' 
and academic_year = '2012' 
order by stu_score desc

输出是

数据库截图

对于表中的其他主题，我需要相同的内容，例如ENGLISH, PHYSICS, CHEMISTRY..... 解决此问题的最佳方法是什么？

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2 回答 2

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如果我很好地理解了您的查询，那么可以在不更改数据库结构的情况下这样做：

select MAIN.stu_number, MAIN.stu_name,  MAIN.ex_name, 
    MATHS.stu_score as MATHEMATICS, 
    ENGLISH.stu_score as ENGLISH, 
    PHYSICS.stu_score as PHYSICS, 
    CHEMISTRY.stu_score as CHEMISTRY
from EXAMS_MASTER_REGISTER MAIN
left join EXAMS_MASTER_REGISTER MATHS on MAIN.stu_number = MATHS.stu_number AND MATHS.ex_subject = 'MATHEMATICS'
left join EXAMS_MASTER_REGISTER ENGLISH on MAIN.stu_number = ENGLISH.stu_number AND ENGLISH.ex_subject = 'ENGLISH'
left join EXAMS_MASTER_REGISTER PHYSICS on MAIN.stu_number = PHYSICS.stu_number AND PHYSICS.ex_subject = 'PHYSICS'
left join EXAMS_MASTER_REGISTER CHEMISTRY on MAIN.stu_number = CHEMISTRY.stu_number AND CHEMISTRY.ex_subject = 'CHEMISTRY'
where MAIN.stu_level = '1' 
and MAIN.stu_stream = 'EAST' 
and MAIN.ex_semester = 'FIRST' 
and MAIN.ex_name = 'MIDYEARS' 
and MAIN.academic_year = '2012' 
order by (NVL(MATHS.stu_score,0) + NVL(ENGLISH.stu_score,0) + NVL(PHYSICS.stu_score,0) + NVL(CHEMISTRY.stu_score,0) ) desc

注意：我更改了顺序，因为在那种形式下它不再可用了，现在这对分数求和，然后按那个排序。

但是，这种确切的数据库结构是不好的。这不是第一范式（1NF），这使事情变得不必要地困难并且容易出错。还可以考虑阅读2NF、3NF和BCNF（其他的也是，但 AFAIK，这些是更广为人知和使用的范式）。我假设您正在学习，这将使您走上正确的轨道。

您应该将一张表分成（至少）两张：一张用于学生的个人数据（现在与 MAIN 别名一起使用的列），一张用于分数（其他列）。

于 2012-10-22T11:09:57.510 回答
2

对于只需要一次访问表的查询，请尝试：

select stu_number, 
       max(stu_name) stu_name, 
       ex_name, 
       max(case when ex_subject = 'MATHEMATICS' then stu_score end) as MATHEMATICS,
       max(case when ex_subject = 'ENGLISH' then stu_score end) as ENGLISH,
       max(case when ex_subject = 'PHYSICS' then stu_score end) as PHYSICS,
       max(case when ex_subject = 'CHEMISTRY' then stu_score end) as CHEMISTRY
from EXAMS_MASTER_REGISTER 
where stu_level = '1' and 
      stu_stream = 'EAST' and 
      ex_semester = 'FIRST' and 
      ex_name = 'MIDYEARS' and 
      academic_year = '2012' 
group by stu_number, ex_name
order by sum(stu_score) desc
于 2012-10-22T11:20:23.447 回答