Question

我的数据集具有以下格式;

Student_id Month Year Amount
1           Jan  2010  600
1           Feb  2010  391
1           Apr  2010  673
1           Jul  2010  564
5           Jan  2010  789
5           Mar  2011  298
5           Aug  2010  347
7           Jan  2010  654
7           Dec  2011  621
7           Apr  2010  450
7           Nov  2011  980

...＆amp;等等。

我希望我的输出对于每个唯一的id-month-year组合具有最大量。即，

Student_id Month Year Amount
1          Apr   2010 673
5          Jan   2010 789
7          Nov   2011 980

...＆amp;像这样。

如何使用SQL获取输出？我试过了

select distinct * , MAX(Amount) from student_details;

＆安培;

SELECT *, MAX(Amount)
FROM student_details
WHERE Amount IN
(
    FROM student_details
    GROUP BY Student_ID, Year, Month
);

但输出不符合要求。

请建议协助。提前谢谢。

Answer 1

在MySQL中：

SELECT t0.*
FROM student_details AS t0
LEFT JOIN student_details AS t1 ON t0.Student_id=t1.Student_id t1.Amount>t0.Amount
WHERE t1.Student_id IS NULL;

在SQL server中：

SELECT T.Student_id,T.Month,T.Year,T.Amount
FROM 
(
   SELECT *,row_number() over (PARTITION BY Student_ID ORDER BY Amount DESC) as RN
   FROM student_details
)T
WHERE T.RN=1

Answer 2

只需使用以下查询

首先为每个用户选择金额月份，然后选择已选择月份的数据

SELECT * FROM table WHERE amount IN (
    SELECT max(amount) FROM table group by student_id
)

从Mysql

2 个答案: