create database stuinfocreate table student(   mid char(10) not null primary key,   mname char(50) not null)create table  course(  fid char(10) not null primary key,  fname char(50) not null)create table score(   sid int identity(1,1) primary key,   fid char(10) not null,   mid char(10) not null,   score int,   foreign key(fid) references course(fid),   foreign key(mid) references student(mid))INSERT INTO course(FID,FName)VALUES('F001','语文') INSERT INTO course(FID,FName)VALUES('F002','数学') INSERT INTO course(FID,FName)VALUES('F003','英语') INSERT INTO course(FID,FName)VALUES('F004','历史') --学生表中插入数据-- INSERT INTO student(MID,MName)VALUES('M001','张萨') INSERT INTO student(MID,MName)VALUES('M002','王强') INSERT INTO student(MID,MName)VALUES('M003','李三') INSERT INTO student(MID,MName)VALUES('M004','李四') INSERT INTO student(MID,MName)VALUES('M005','阳阳') INSERT INTO student(MID,MName)VALUES('M006','虎子') iNSERT INTO student(MID,MName)VALUES('M007','夏雪') INSERT INTO student(MID,MName)VALUES('M008','璐璐') INSERT INTO student(MID,MName)VALUES('M009','珊珊') INSERT INTO student(MID,MName)VALUES('M010','香奈儿')INSERT INTO Score(FID,MID,Score)VALUES('F001','M001',78) INSERT INTO Score(FID,MID,Score)VALUES('F002','M001',67) INSERT INTO Score(FID,MID,Score)VALUES('F003','M001',89) INSERT INTO Score(FID,MID,Score)VALUES('F004','M001',76) INSERT INTO Score(FID,MID,Score)VALUES('F001','M002',89) INSERT INTO Score(FID,MID,Score)VALUES('F002','M002',67) INSERT INTO Score(FID,MID,Score)VALUES('F003','M002',84) INSERT INTO Score(FID,MID,Score)VALUES('F004','M002',96) INSERT INTO Score(FID,MID,Score)VALUES('F001','M003',70) INSERT INTO Score(FID,MID,Score)VALUES('F002','M003',87) INSERT INTO Score(FID,MID,Score)VALUES('F003','M003',92) INSERT INTO Score(FID,MID,Score)VALUES('F004','M003',56) INSERT INTO Score(FID,MID,Score)VALUES('F001','M004',80) INSERT INTO Score(FID,MID,Score)VALUES('F002','M004',78) INSERT INTO Score(FID,MID,Score)VALUES('F003','M004',97) INSERT INTO Score(FID,MID,Score)VALUES('F004','M004',66) INSERT INTO Score(FID,MID,Score)VALUES('F001','M006',88) INSERT INTO Score(FID,MID,Score)VALUES('F002','M006',55)INSERT INTO Score(FID,MID,Score)VALUES('F003','M006',86) INSERT INTO Score(FID,MID,Score)VALUES('F004','M006',79) INSERT INTO Score(FID,MID,Score)VALUES('F002','M007',77) INSERT INTO Score(FID,MID,Score)VALUES('F003','M008',65) INSERT INTO Score(FID,MID,Score)VALUES('F004','M007',48) INSERT INTO Score(FID,MID,Score)VALUES('F004','M009',75) INSERT INTO Score(FID,MID,Score)VALUES('F002','M009',88)   select * from scoreselect mname,语文=             max(case               when course.fname='语文' then score.score             end)            ,数学=             max(case               when course.fname='数学' then score             end)            ,英语=max(case               when course.fname='英语' then (score)             end)            ,历史=max(case               when course.fname='历史' then (score)             end)from student,score,course where student.mid=score.mid and score.fid=course.fidgroup by mnameselect   姓名=mname,课程=fname,成绩=score  from student,course,score where score<70 and student.mid=score.mid and score.fid=course.fidselect 姓名=(select mname from student where mid=score.mid ),       课程=(select fname from course where fid=score.fid),       成绩=scorefrom score where score<70--select * from score where score<70select 姓名=(select mname from student where mid=score.mid),平均分=avg(score)  from score group by mid order by 平均分 descselect distinct mid from score select mid from student