显示重复的最大值

Question

我有一个表：

+----------------+----------------+------------------+-------+ 
| Student_Id | Student_Name | Assessment_Type | Mark | 
+----------------+----------------+------------------+-------+ 
| 300   |  John  | Assignment  | 1 | 
| 200   |  Liz  | Final   | 2 | 
| 300   |  John  | Mid-term  | 3 | 
| 100   |  Sue  | Mid-term  | 4 | 
| 200   |  Liz  | Project  | 5 | 
| 300   |  John  | Assignment  | 6 | 
| 200   |  Liz  | Final   | 7 | 
| 300   |  John  | Mid-term  | 8 | 
| 100   |  Sue  | Mid-term  | 8 | 
| 200   |  Liz  | Project  | 9 | 
+----------------+----------------+------------------+-------+ 

我想找到Assessment_Type分组的最大标志，如果有重复的，同时显示，所以在这种情况下：

+----------------+----------------+------------------+-------+ 
| Student_Id | Student_Name | Assessment_Type | Mark | 
+----------------+----------------+------------------+-------+ 
| 300   |  John  | Assignment  | 6 | 
| 200   |  Liz  | Final   | 7 | 
| 300   |  John  | Mid-term  | 8 | 
| 100   |  Sue  | Mid-term  | 8 | 
| 200   |  Liz  | Project  | 9 | 
+----------------+----------------+------------------+-------+ 

我只显示其中之一：

SELECT Student_Id, Student_Name, Assessment_Type, max(mark) FROM STUDENT_ASSESSMENT group by Student_Id, Assessment_Type; 

编辑：增加了更多的细节问题。

Answer 1

你可以找到最大的标记在每个评估类型，然后比较最大值（马克）和每行的评估类型。

select * from STUDENTS_ASSESSMENT where (Assessment_Type,marks) in 
((select Assessment_Type,max(marks) from STUDENTS_ASSESSMENT groupby Assessment_Type)); 

Answer 2

你可以找到Mark列的最大值，然后选择行认为Mark值等于该值：

SELECT 
    Student_Id, Student_Name, Assessment_Type, Mark 
FROM 
    STUDENT_ASSESSMENT FullSet 
JOIN 
    (SELECT MAX(Mark) AS Mark FROM STUDENT_ASSESSMENT) MaxMark 
USING (Mark);