Question

写一个查询以显示科目名称和学生姓名，这些科目名称和学生姓名在按subject_name升序排列的每个科目中获得最高分。该解决方案必须在子查询中实现。

我已使用以下查询：

 select subject_name, student_name
 from subject s
 inner join mark m
 on s.subject_id=m.subject_id
 inner join student s1
  on m.student_id=s1.student_id
  where student_id in  (select student_id
                          from mark
                         having max(value)
                          group by s.subject_id)
  order by s.subject_name;

但是此代码在无效的关系运算符的第10行给出了错误

请帮助！

Answer 1

尝试以下

SELECT
    SB.SUBJECT_NAME,
    S.STUDENT_NAME
FROM
    STUDENT S,
    SUBJECT SB,
    (
        SELECT
            STUDENT_ID,
            SUBJECT_ID,
            MARKS
        FROM
            MARKS
        WHERE
            ( SUBJECT_ID,
              MARKS ) IN (
                SELECT
                    M.SUBJECT_ID,
                    MAX(M.MARKS)
                FROM
                    MARKS M
                GROUP BY
                    M.SUBJECT_ID
            )
    ) MM
WHERE
    S.STUDENT_ID = MM.STUDENT_ID
    AND SB.SUBJECT_ID = MM.SUBJECT_ID;

Demo

谢谢

Answer 2

使用聚合函数时，必须使用子句HAVING来添加条件，因为where子句不允许使用该语法，

**SELECT columns FROM table_name WHERE condition GROUP BY columns HAVING condition**

例如存在条件的情况： max（value）> 1000

您的子查询应如下所示：

SELECT student_id, max(value)
FROM   mark
WHERE  student_id = s.subject_id
GROUP BY student_id
HAVING  MAX(value) > 1000;

致谢！

查找在每个学科中获得最高分的学生的姓名

2 个答案: