mysql - 如何做这个sql查询？

Question

架构:

Student(studentid,name,age)
Course(coursename,dept)
enroll(studentid,coursename,grade)

我需要编写 sql 来查找每个年龄段的学生姓名，以及从历史和政治科学系选修的类(class)的最高分。

到目前为止我的尝试是

SELECT 
    name 
FROM 
    student 
GROUP BY age 
HAVING sid IN 
            (
                SELECT 
                    max(grade) 
                FROM 
                    enroll e,enroll e1 
                WHERE 
                    e.studentid = e1.studentid 
                AND e.coursename = (
                                    SELECT coursename FROM course 
                                    WHERE 
                                        dname like '%History%'
                                  ) 
                AND e1.coursename = (
                                    SELECT coursename FROM course 
                                    WHERE 
                                        dname like '%PoliticalScience%'
                                    )
            )

Answer 1

您可以使用子查询 获取最高分。试试看，

SELECT  d.*,
        f.dept,
        e.grade
FROM    student d
        INNER JOIN enroll e
            on d.studentID = e.studentID
        INNER JOIN course f
            ON e.courseName = f.courseName
        INNER JOIN
            (
                SELECT  a.age, c.dept, Max(b.grade) maxGrade
                FROM    student a
                        INNER JOIN enroll b
                            on a.studentID = b.studentID
                        INNER JOIN course c
                            ON b.courseName = c.courseName
                WHERE    c.dept IN ('history','political science')
                GROUP BY a.age, c.dept
            ) topScore
            ON  topscore.age = d.age AND
                topscore.dept = f.dept AND
                topscore.maxGrade = e.grade