如何選擇具有最大價值

Question

我有一個Access數據庫，其中包含一個Grads表：

Grads 
- studentId 
- courseId 
- tryNumber 
- semesterId 
- finalGrad 

如何獲得所有的信息（studentName, courseName, courseId, finalGrade）從最大tryNumber（最後一次嘗試）行？

Answer 1

如果你只想要一個行與max trynumber，然後你應該可以使用：

select g.studentid, 
    g.courseid, 
    g.trynumber, 
    g.semesterid, 
    g.finalgrade 
from grads g 
inner join 
(
    select max(tryNumber) MaxTry 
    from grads 
) m 
    on g.trynumber = m.maxtry 

如果你想返回每個學生的max(tryNumber)，那麼你可以使用：

select g.studentid, 
    g.courseid, 
    g.trynumber, 
    g.semesterid, 
    g.finalgrad 
from grads g 
inner join 
(
    select studentid, max(tryNumber) MaxTry 
    from grads 
    group by studentid 
) m 
    on g.trynumber = m.maxtry 
    and g.studentid = m.studentid 

Answer 2

這應該爲你工作：

SELECT studentName, 
     courseName, couseId, 
     finalGrade, MAX(tryNumber) 
FROM grads 
GROUP BY studentName, courseName, couseId, finalGrade 

Answer 3

select top 1 * from Grads order by tryNumber desc

Answer 4

您可以使用：

Select studentName, courseName, courseId, finalGrade From Grads 
Where tryNumber=(Select MAX(tryNumber) From Grads)