数据库要做

drop table if exists Student;
create table Student (
Sid varchar(5) primary key,
Sname varchar(10),
Sage int(3),
Ssex varchar(10)
);
drop table if exists Course;
create table Course(
Cid varchar(5)  primary key,
Cname varchar(10),
Tid int(5)
);
drop table if exists SC;
create table SC(
Sid varchar(5)  primary key,
Cid varchar(5),
score double(4,1)
);
drop table if exists Teacher;
create table Teacher(
Tid varchar(5)  primary key,
Tname varchar(10)
);
十几道sql语句面试题第1部分：
Student(Sid, Sname, Sage, Ssex)学生表
Course(Cid, Cname, Tid)课程表
SC(Sid, Cid, score)成绩表
Teacher(Tid, Tname)教师表
问题：
1、查询“001”课程比“002”课程成绩高的所有学生的学号；
select a.Sid from (select Sid, score from SC where Cid = ’001′) a,
(select Sid, score from SC where Cid = ’002′) b where a.score > b.score and a.Sid = b.Sid;
2、查询平均成绩大于60分的同学的学号和平均成绩；
select  Sid,
avg(score)  from  sc  group   by  Sidhavingavg(score) > 60;
3、查询所有同学的学号、姓名、选课数、总成绩；
select Student.Sid,
Student.Sname,
count(SC.Cid),
sum(score)  from Student left Outer join SConStudent.Sid = SC.Sid group  by Student.Sid,
Sname4、查询姓“李”的老师的个数；select count(distinct(Tname))  from Teacher where Tnamelike‘李 % ’;
5、查询没学过“叶平”老师课的同学的学号、姓名；
select Student.Sid,
Student.Sname from Student
where Sid not in
        (select distinct(SC.Sid)
            from SC, Course, Teacher
            where SC.Cid = Course.Cid and Teacher.Tid = Course.Tid and Teacher.Tname = ’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 Student.Sid,
Student.Sname from Student,SC
where Student.Sid = SC.Sid and SC.Cid = ’001′ and exists
    (select  *  from SC   as   SC_2
        where SC_2.Sid = SC.Sid and SC_2.Cid = ’002′);
7、查询学过“叶平”老师所教的所有课的同学的学号、姓名；
select Sid,Sname
from Student
8、查询所有课程成绩小于60分的同学的学号、姓名；
select Sid,Sname
from Student
where Sid notin
        (select Student.Sid
        from Student, SC
        where S.Sid = SC.Sid and score > 60);
9、查询没有学全所有课的同学的学号、姓名；
select Student.Sid,Student.Sname
from Student,SC
where Student.Sid = SC.Sid group  by Student.Sid,Student.Sname
having count(Cid) < (select count(Cid)  from Course);
10、查询至少有一门课与学号为“1001”的同学所学相同的同学的学号和姓名；
select Sid,
Sname from Student,
SC where Student.Sid = SC.Sid and Cid in
（select Cid from SC where Sid = ‘1001‘）;
11、删除学习“叶平”老师课的SC表记录；
delect  SC from course,
Teacher where Course.Cid = SC.Cid and Course.Tid = Teacher.Tid and Tname = ‘叶平‘;
12、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分
select L.Cid课程ID,
L.score最高分,
R.score最低分 from SCL,SCR
where L.Cid = R.Cid and L.score =
    (select MAX(IL.score)
    from SCIL, StudentIM
    where IL.Cid = L.Cid and IM.Sid = IL.Sid group  by IL.Cid)  and R.Score =
        (select MIN(IR.score)  from SCIR where IR.Cid = R.Cid group  by IR.Cid);
13、查询学生平均成绩及其名次
select 1 + (select COUNT(distinct平均成绩)
from
        (select Sid, AVG(score)平均成绩
        from SC group  by Sid) T1
        where 平均成绩 > T2.平均成绩)名次,Sid学生学号,平均成绩
        from (select Sid, AVG(score)平均成绩 from SC group  by Sid) T2   order   by 平均成绩desc;
14、查询各科成绩前三名的记录: (不考虑成绩并列情况)
 select t1.Sid  as  学生ID,t1.Cid  as  课程ID,Score  as  分数
from SCt1 where scoreIN
        (select TOP3score
        from SC
        where t1.Cid = Cid   order   by scoreDESC)   order   by t1.Cid;
15、查询每门功成绩最好的前两名
select t1.Sid  as  学生ID,t1.Cid  as  课程ID,Score  as  分数
from SCt1
where scoreIN
        (select TOP2score
        from SC
        where t1.Cid = Cid  order   by scoreDESC)   order   by t1.Cid;