sql地址:https://www.jianshu.com/p/476b52ee4f1b

    练习1:
    — 1:查询” 01 “课程比” 02 “课程成绩高的学生的信息及课程分数
    select student.SId,student.Sage,student.Sname,student.Ssex , Re.c1Score,Re.c2Score from student
    join
    (select c1.sid,c1.c1Score,c2.c2Score from
    (select sid , score As c1Score from sc left join course on sc.CId=course.CId and course.cid=01 group by sid) AS c1
    join
    (select sid , score As c2Score from sc left join course on sc.cid=course.CId and course.cid =02 group by sid)AS c2
    on c1.sid=c2.sid
    and c1.c1Score>c2.c2Score) As Re
    on student.sid = Re.sid
    image.png

    练习2:
    1.1 查询同时存在” 01 “课程和” 02 “课程的情况
    select c1.sid,c1.c1Score,c2.c2Score from
    (select sid , score As c1Score from sc left join course on sc.CId=course.CId and course.cid=01 group by sid) AS c1
    join
    (select sid , score As c2Score from sc left join course on sc.cid=course.CId and course.cid =02 group by sid)AS c2
    on c1.sid=c2.sid
    image.png