Oracle基础查询

create table student
(
  sno varchar2(10) primary key,
  sname varchar2(20),
  sage number(2),
  ssex varchar2(5)
);

create table teacher
(
  tno varchar2(10) primary key,
  tname varchar2(20)
);

create table course
(
  cno varchar2(10),
  cname varchar2(20),
  tno varchar2(20),
  constraint pk_course primary key (cno,tno)
);

create table sc
(
  sno varchar2(10),
  cno varchar2(10),
  score number(4,2), 
  constraint pk_sc primary key (sno,cno)
);

--初始化学生表的数据
insert into student values ('s001','张三',23,'男');
insert into student values ('s002','李四',23,'男');
insert into student values ('s003','吴鹏',25,'男');
insert into student values ('s004','琴沁',20,'女');
insert into student values ('s005','王丽',20,'女');
insert into student values ('s006','李波',21,'男');
insert into student values ('s007','刘玉',21,'男');
insert into student values ('s008','萧蓉',21,'女');
insert into student values ('s009','陈萧晓',23,'女');
insert into student values ('s010','陈美',22,'女');

commit

--初始化教师表
insert into teacher values ('t001', '刘阳');
insert into teacher values ('t002', '谌燕');
insert into teacher values ('t003', '胡明星');

commit

--初始化课程表
insert into course values ('c001','J2SE','t002');
insert into course values ('c002','Java Web','t002');
insert into course values ('c003','SSH','t001');
insert into course values ('c004','Oracle','t001');
insert into course values ('c005','SQL SERVER 2005','t003');
insert into course values ('c006','C#','t003');
insert into course values ('c007','JavaScript','t002');
insert into course values ('c008','DIV+CSS ','t001');
insert into course values ('c009','PHP ','t003');
insert into course values ('c010','EJB3.0','t002');

commit

--初始化成绩表
insert into sc values ('s001','c001',78.9);
insert into sc values ('s002','c001',80.9);
insert into sc values ('s003','c001',81.9);
insert into sc values ('s004','c001',60.9);
insert into sc values ('s001','c002',82.9);
insert into sc values ('s002','c002',72.9);
insert into sc values ('s003','c002',81.9);
insert into sc values ('s001','c003','59');

commit

--1、查询姓“李”的学生的详细信息
select * from student where sname like '李%'

--2、查询20-23岁的男同学有多少个
select count(*) from student where ssex='男' and sage between 20 and 23

--3、查询姓“刘”的老师有多少个
select count(*) from teacher where tname like '刘%'

--4、查询男生、女生人数（一条SQL）
select 
  sum(case when ssex='男' then 1 else 0 end)男生,
  sum(case when ssex='女' then 1 else 0 end)女生
from student

--5、查询'刘阳'老师所教的课程
select cname from course where tno in
(select tno from teacher where tname='刘阳')

--6、查找学员编号为's004','s007','s008'的学生信息
select * from student where sno in('s004','s007','s008')

--7、查找教'Oracle'课程的老师
select tname from teacher where tno in
(select tno from course where cname='Oracle')

--8、查找成绩低于60分的课程名称
select cname from course where cno in
(select cno from sc where score<60)

--9、查找成绩良好（分数>80）的学员名称和课程名称

select cname from course where cno in
(select cno from sc where score>80)

select sname from student where sno in
(select sno from sc where score>80)

--10、查询平均成绩大于60 分的同学的学号和平均成绩
select student.sno,t1.avgscore from student INNER JOIN 
(
       select sc.sno ,AVG(sc.score) as avgscore from sc 
       GROUP BY sc.sno HAVING AVG(sc.score)>60
) t1 on student.sno=t1.sno

--11、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 distinct A.cno,最高分,最低分 from sc A
left join course on A.cno=course.cno
left join (select cno,MAX(score)最高分,MIN(score)最低分 from sc group by cno) B on A.cno=B.cno

--12、查询同名同姓学生名单，并统计同名人数
select A.*,B.同名人数 from student A
left join (select sname,ssex,count(*)同名人数 from student group by sname,ssex)B 
on A.sname=B.sname and A.ssex=B.ssex
where B.同名人数>1

--13、1999 年出生的学生名单(注：Student 表中Sage 列的类型是number)
select * from student where to_char(sage)=1999

--14、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列
select sc.cno,avg(sc.score) from sc group by sc.cno order by avg(sc.score) asc,sc.cno desc

--15、查询课程名称为“Oracle”，且分数低于60 的学生姓名和分数
select student.sname,t1.score from student
inner join
(
      select sc.sno,sc.score from sc,course 
      where sc.cno=course.cno and course.cname='Oracle' and sc.score<60
) t1
on student.sno=t1.sno

--16、查询所有学生的选课情况
select student.sname,course.*
from student,course,sc where student.sno=sc.sno and course.cno=sc.cno

--17、查询不及格的课程，并按课程号从大到小排列
select DISTINCT sc.cno from sc where sc.score <60 order by sc.cno desc

--18、查询课程编号为c001 且课程成绩在80 分以上的学生的学号和姓名；
select student.sno,student.Sname from student,sc 
where sc.cno='c001' and student.sno=sc.sno and sc.score>80


--19、求选了课程的学生人数
select count(sno) from student where sno in
(select sno from sc group by sno having count(cno)>=1)

--20、查询各个课程及相应的选修人数
select sc.cno as 课程编号,count(*) as 选修人数 from sc group by sc.cno
having count(*)>0

--思考题：
--21、查询不同课程成绩相同的学生的学号、课程号、学生成绩
select C.sno,max(C.cno)cno,max(C.score)score from sc C 
left join(select sno,avg(score)A from sc group by sno)B 
on C.sno=B.sno
where C.score=B.A
group by C.sno
having COUNT(0)=(select COUNT(0)from sc where sno=C.sno)

--22、检索“c004”课程分数小于60，按分数降序排列的同学学号
select sno from sc where cno='c004' and score<60 order by score desc

--23、查询“c001”课程比“c002”课程成绩高的所有学生的学号；
select A.sno from (select * from sc where cno='c001')A 
left join(select * from sc where cno='c002')B 
on A.sno=B.sno 
where A.score>B.score

--24、查询没学过“谌燕”老师课的同学的学号、姓名；
select sno,sname from Student where sno in
(select distinct sno from sc where cno in
(select cno from course where tno=
(select tno from teacher where tname='谌燕')))

--25、按各科平均成绩从低到高和及格率的百分数从高到低顺序
select sc.cno as 课程id,avg(sc.score) as 平均成绩,
100*sum(case when sc.score>=60 then 1 else 0 end)/count(1)||'%' as 及格率
from sc
group by sc.cno
order by avg(sc.score),
sum(case when sc.score>=60 then 1 else 0 end)/count(1) desc;