选择一列的 SUM 并获取其他列的数量

Question

我有一张像

student_id  student_name    subject marks
1              A            a_sub   10
1              A            a_sub   10
2              A            b_sub   5
3              A            c_sub   20
4              B            b_sub   10

从我想从哪里获取SUM(marks)和所有其他列的 ex, SELECT student_name, subject, SUM(marks) AS marks FROM records ORDER BY student_id 。

结果应该是这样的：

student_name    subject marks
A               a_sub   45
B               b_sub   10

我尝试使用GROUP BY但它不起作用，因为student_name具有不同的subject值

Answer 1

如果您只想要“第一个”主题，则可以使用min()并按名称分组。

SELECT student_name, min(subject) as subject, SUM(marks) AS marks 
FROM records 
GROUP BY student_name
ORDER BY student_name;

Answer 2

您可以使用此查询获取输出

select distinct b.student_name, b.marks, (select top 1 subject from [records] where b.student_name = student_name)
from [records] a
inner join (
        SELECT student_name, SUM(marks) AS marks 
        FROM [records] 
        GROUP BY student_name) b on a.student_name = b.student_name
ORDER BY b.student_name

我也尝试过它的工作正常

Answer 3

您可以使用窗口函数：

select distinct r.student_name, 
       first_value(r.subject) over (partition by r.student_name order by r.student_id) as subject,
       sum(r.marks) oever (partition by r.student_name) as marks
from records r;

简单聚合也可以：

select student_name, min(subject) as subject, sum(marks) as marks 
from records r 
group by student_name;