sql - TSQL : Max date but include other variables

Question

我正在尝试查找具有最大日期的记录，这很简单，但是当我想要其他属性时它不起作用。

我有 3 张 table 。

表 1 = 学生。

Columns STid, STname
Value    1, John
         2, Bob Lee
         3, Jane

表 2 = 测试。

Columns Testid, STid, Date, Grade
Value    1, 1, 20/05/2018, A
         2, 2, 20/05/2018, B
         3, 3, 20/05/2018, D
         4, 1, 30/06/2018, C
         5, 2, 30/06/2018, C
         6, 3, 30/06/2018, B

我想要的是每个学生上次测试的成绩。

输出应该是..

Columns STname, Date, Grade
Value    John, 1, 30/06/2018, C
         Bob Lee, 2, 30/06/2018, C
         Jane, 3, 30/06/2018, B

当我尝试以下操作时，它工作正常，但我需要成绩。

SELECT STNAME, MAX(T.DATE)
FROM STUDENT S, TEST T
WHERE S.STID = T.STID
GROUP BY STNAME

不幸的是，下面的方法不起作用。

SELECT STNAME, MAX(T.DATE), T.GRADE
FROM STUDENT S, TEST T
WHERE S.STID = T.STID
GROUP BY STNAME

或者下面只是带回所有内容。

SELECT STNAME, MAX(T.DATE), T.GRADE
FROM STUDENT S, TEST T
WHERE S.STID = T.STID
GROUP BY STNAME, T.GRADE.

我怀疑答案在于子查询，但我也无法让它工作。

SELECT STNAME, T.DATE, T.GRADE
FROM STUDENT S, TEST T
WHERE S.STID = T.STID
AND T.DATE = (SELECT MAX(T.DATE)
             FROM STUDENT S, TEST T
             WHERE S.STID = T.STID )

OR 

SELECT STNAME, T.DATE, T.GRADE
FROM STUDENT S, TEST T
WHERE S.STID = T.STID
AND T.DATE = (SELECT MAX(T2.DATE)
             FROM STUDENT S2, TEST T2
             WHERE S.STID = S2.STID )

感谢任何帮助。

Answer 1

您需要row_number()函数:

select t.*
from (select s.stid, s.STname, t.Date, t.Grade, 
             row_number() over (partition by s.stid order by t.date desc) as seq
      from student s inner join
           test t
           on t.stid = s.stid
      ) t
where seq = 1;