1. 选出每门功课都及格的学号 select distinct `s#` from sc where `s#` not in (select `s#` from sc where score 60) 2. 查询“1”课程比“2”课程成绩高的所有学生的学号； SELECT c01.`s#` from (select `s#`, `score` from sc where `c#`=1) c01, (select `s#`, `score` from sc where `c#`=2) c02 where c01.`s#` = c02.`s#` and c01.score > c02.score 3. 查询平均成绩大于60分的同学的学号和平均成绩； select `s#`, avg(score) from sc group by `s#` having avg(score) > 60 4. 查询所有同学的学号、姓名、选课数、总成绩； select student.`s#`, student.`Sname`, count(`c#`), sum(score) from student left outer join sc on student.`s#` = sc.`s#` group by student.`s#`, sc.`s#`
5.查询没学过“叶平”老师课的同学的学号、姓名； select student.`s#`, student.`Sname` from student where student.`s#` not in (select distinct(sc.`s#`) from teacher, course, sc where Tname='叶平' and teacher.`t#` = course.`t#` and sc.`c#`= course.`c#` ) 6. 查询学过“001”并且也学过编号“002”课程的同学的学号、姓名 select student.`s#`, student.sname from student, sc where student.`s#` = sc.`s#` and sc.`c#` = 1 and exists (select * from sc sc_2 where sc_2.`c#`=2 and sc.`s#`=sc_2.`s#`) 7. 查询学过“叶平”老师所教的所有课的同学的学号、姓名 (巧妙) select `s#`, sname from student where `s#` in (select `s#` from sc, teacher, course where tname='叶平' and teacher.`t#`=course.`t#` and course.`c#`= sc.`c#` group by `s#` having count(sc.`c#`)= (select count(`c#`) from teacher, course where tname='叶 平' and teacher.`t#`=course.`t#`) )
8. 查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名 (有代表性) select `s#`, sname from (select student.`s#`, student.sname, score, (select score from sc sc_2 where student.`s#`=sc_2.`s#` and sc_2.`c#`=2) score2 from student , sc where sc.`s#`=student.`s#` and sc.`c#`=1) s_2 where score2 score 9.查询没有学全所有课的同学的学号、姓名 select student.`S#`, Sname from student, sc where student.`s#` = sc.`s#` group by `s#`, sname having count(`c#`) (select count(`c#`) from course)
10. 查询至少有一门课与学号为“002”的同学所学相同的同学的学号和姓名； select distinct(sc.`s#`), sname from student, sc where student.`s#`=sc.`s#` and `c#` in (select `c#` from sc where `s#`=002) 11. 把“SC”表中“叶平”老师教的课的成绩都更改为此课程的平均成绩；
update sc inner join (select sc2.`c#`, avg(sc2.score) score from sc sc2, teacher, course where sc2.`c#`=course.`c#` and tname='叶平' and teacher.`t#` = course.`t#` and course.`c#`=sc2.`c#` group by course.`c#`) sc3 on sc.`c#`=sc3.`c#` set sc.score=sc3.score 12. 查询2号的同学学习的课程他都学了的同学的学号；（注意理解：where语句的 第一个条件过滤掉不满足c#的记录，再group by，就比较清晰） select `S#` from SC where `C#` in (select `C#` from SC where `S#`=2) group by `S#` having count(*)=(select count(*) from SC where `S#`=2);
