Question

我有一个包含3列的表格，分别是“年”，“ students_count”和“ faculty”。我想找出每个教员最多的“ students_count”数。

该表如下所示：

year| students_count| faculty
------------------------------------
2001| 50            | Business
2002| 60            | Business
2003| 40            | Business
2001| 20            | Engineering
2002| 10            | Engineering
2003| 50            | Law

SELECT year,max(students_count),faculty FROM table;

（不起作用）

year| students_count| faculty
-----------------------------------
2002| 60            | Business
2001| 20            | Engineering
2003| 50            | Law

Answer 1

使用row_number()

select * from
(
select *,row_number() over(partition by faculty order by students_count desc) as rn
from tablename 
)A where rn=1

Answer 2

如果需要，可以按年和教职员工的最大需求分组。

SELECT year,max(students_count),faculty FROM table group by year,faculty

但是如果只需要教师，则可以使用相关的子查询

select top (1) with ties t.*
from table_name t
order by row_number() over (partition by faculty order by students_count   desc)

Answer 3

您想要dense_rank()：

select t.*
from (select t.*,
             dense_Rank() over (partition by faculty order by students_count desc) as seq
      from table t
     ) t
where seq = 1;

Answer 4

这可以做到：

select * from (select *,rank() over (partition by faculty order by sytudents_count desc 
) rnk form tablename) where rnk=1;

Answer 5

为此，我认为您只需要在sql中使用group by。这也许可以解决这个问题。

Create Table School(
Year Number(4),
Students_Count Number(2),
Faculty Varchar2(20)
);

Insert Into School  Values (2001,50,'Business');
Insert Into School  Values (2002,60,'Business');
Insert Into School  Values (2003,40,'Business');
Insert Into School  Values (2001,20,'Engineering');
Insert Into School  Values (2002,10,'Engineering');
Insert Into School  Values (2003,50,'Law');

Select * From School;

Select  Faculty,Max(Students_Count) From School
Group By Faculty;

如何根据另一个属性的值选择最大数量？

5 个答案: