–（1）查询“001”课程比“002”课程成绩低的所有学生的学号、001学科成绩、002学科成绩
select s1.studentno,s1.score,s2.score from score s1 ,score s2where s1.courseno=1 and s2.courseno = 2 and s1.studentno = s2.studentno and s1.score 60GO–（3）查询所有同学的学号、姓名、选课数、总成绩
select stu.name,stu.studentno,COUNT(sco.CourseNo),SUM(sco.score) from student stu , score sco where stu.studentno = sco.StudentNo group by stu.StudentNo,stu.name–（4）查询姓“李”的老师的个数
select COUNT(1) as total from teacher where name like '叶%'–（5）查询没学过“叶平”老师课的同学的学号、姓名 – 报了叶平老师的学号
select s.name,s.studentno from student s where s.studentNo in(select distinct StudentNo from score sc, course c , teacher tea where sc.CourseNo = c.courseNo and c.teacherNo = tea.teacherNo and tea.name = '叶平')– （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 stu.studentno,stu.name,COUNT(sc.CourseNo) from student stu,score scwhere stu.studentno = sc.StudentNoand sc.CourseNo in (1,2)group by stu.studentno,stu.name having COUNT(sc.CourseNo) >1– （7）查询学过“叶平”老师所教的所有课的同学的学号、姓名 –首先是求出叶平老师的课程数量
select * from student where studentno in (select sco.StudentNo from course c,score sco,teacher te where c.teacherNo = te.teacherno and c.CourseNo = sco.CourseNo and te.name='叶平' group by sco.StudentNo having COUNT(1) =(select COUNT(1) from course where teacherno in (select tea.teacherno from teacher tea where tea.name = '叶平')))– （8）查询有课程成绩小于60分的同学的学号、姓名
SELECT DISTINCT s1.StudentNo, stu1.nameFROM score s1, student stu1WHERE s1.StudentNo = stu1.studentNo AND s1.score