MySQL全方位練習（學生表 教師表 課程表 分數表）

一、創建表並初始化數據

1、表說明

  student(學生表)、teacher(教師表)、course(課程表)、sc(分數表)

2、創建表

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

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

//課程表
create table course(  
   cno varchar2(10),  
   cname varchar2(20),  
   tno varchar2(20),  
   constraint pk_course primary key (cno,tno)  
); 
 
//分數表
create table sc(  
   sno varchar2(10),  
   cno varchar2(10),  
   score number(4,2),  
   constraint pk_sc primary key (sno,cno)  
);  

3、插入初始化數據

/*******初始化學生表的數據******/  
insert into student values ('s001','張三',23,'男');  
insert into student values ('s002','李四',23,'男');  
insert into student values ('s003','吳鵬',25,'男');  
insert into student values ('s004','琴沁',20,'女');  
insert into student values ('s005','王麗',20,'女');  
insert into student values ('s006','李波',21,'男');  
insert into student values ('s007','劉玉',21,'男');  
insert into student values ('s008','蕭蓉',21,'女');  
insert into student values ('s009','陳蕭曉',23,'女');  
insert into student values ('s010','陳美',22,'女');  
commit;  

/******************初始化教師表***********************/  
insert into teacher values ('t001', '劉陽');  
insert into teacher values ('t002', '諶燕');  
insert into teacher values ('t003', '胡明星');  
commit;  

/***************初始化課程表****************************/  
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;  

/***************初始化成績表***********************/  
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;  

二、SQL語句

1、查詢“c001”課程比“c002”課程成績高的所有學生的學號；

select a.* from
 (select * from sc a where a.cno='c001') a,
 (select * from sc b where b.cno='c002') b
 where a.sno=b.sno and a.score > b.score;

或

select * from sc a
 where a.cno='c001' 
 and  exists(select * from sc b where b.cno='c002' and a.score>b.score and a.sno = b.sno)

******************************************************************

2、查詢平均成績大於60 分的同學的學號和平均成績；

select sno,avg(score) from sc  group by sno having avg(score)>60;

******************************************************************

3、查詢所有同學的學號、姓名、選課數、總成績；

select a.*,s.sname from (select sno,sum(score),count(cno) from sc group by sno) a ,student s where a.sno=s.sno

******************************************************************

4、查詢姓“劉”的老師的個數；

select count(*) from teacher where tname like '劉%';

******************************************************************

5、查詢沒學過“諶燕”老師課的同學的學號、姓名；

select a.sno,a.sname from student a where a.sno not in
(
 select distinct s.sno from sc s,
      (
       select c.* from course c ,
           (select tno from teacher t where tname='諶燕') t
       where c.tno=t.tno
      ) b
  where s.cno = b.cno 
)
或
select * from student st where st.sno not in
(
 select distinct sno from sc s 
 join course c on s.cno=c.cno
 join teacher t on c.tno=t.tno where tname='諶燕'
)

******************************************************************

6、查詢學過“c001”並且也學過編號“c002”課程的同學的學號、姓名；

select st.* from sc a 
 join sc b on a.sno=b.sno
 join student st on st.sno=a.sno
 where a.cno='c001' and b.cno='c002' and st.sno=a.sno;

******************************************************************

7、查詢學過“諶燕”老師所教的所有課的同學的學號、姓名；

select st.* from student st join sc s on st.sno=s.sno
 join course c on s.cno=c.cno
 join teacher t on c.tno=t.tno
 where t.tname='諶燕'

******************************************************************

8、查詢課程編號“c002”的成績比課程編號“c001”課程低的所有同學的學號、姓名；

select * from student st
 join sc a on st.sno=a.sno
 join sc b on st.sno=b.sno
 where a.cno='c002' and b.cno='c001' and a.score < b.score
******************************************************************

9、查詢所有課程成績小於60 分的同學的學號、姓名；

select st.*,s.score from student st
 join sc s on st.sno=s.sno
 join course c on s.cno=c.cno
 where s.score <60

******************************************************************

10、查詢沒有學全所有課的同學的學號、姓名；

select stu.sno,stu.sname,count(sc.cno) from student stu
 left join sc on stu.sno=sc.sno
 group by stu.sno,stu.sname
 having count(sc.cno)<(select count(distinct cno)from course)

或
select * from student where sno in
(
 select sno from
        (
         select stu.sno,c.cno from student stu cross join course c minus select sno,cno from sc
        )
)

******************************************************************

11、查詢至少有一門課與學號為“s001”的同學所學相同的同學的學號和姓名；

select st.* from student st,
 (select distinct a.sno from
  (select * from sc) a,
  (select * from sc where sc.sno='s001') b
  where a.cno=b.cno
 ) h
 where st.sno=h.sno and st.sno<>'s001'

******************************************************************

12、查詢至少學過學號為“s001”同學所有一門課的其他同學學號和姓名；

select * from sc
 left join student st on st.sno=sc.sno
 where sc.sno<>'s001' 
 and sc.cno in (select cno from sc where sno='s001')

******************************************************************

13、把“SC”表中“諶燕”老師教的課的成績都更改為此課程的平均成績；

update sc c set score=
 (
  select avg(c.score)  from course a,teacher b 
  where a.tno=b.tno and b.tname='諶燕' and a.cno=c.cno 
  group by c.cno
 )
where cno in( select cno from course a,teacher b where a.tno=b.tno and b.tname='諶燕')

******************************************************************

14、查詢和“s001”號的同學學習的課程完全相同的其他同學學號和姓名；

select* from sc where sno<>'s001'
minus
( select* from sc minus select * from sc where sno='s001')

******************************************************************

15、刪除學習“諶燕”老師課的SC 表記錄；

delete from sc where sc.cno in
(
 select cno from course c
 left join teacher t on  c.tno=t.tno
 where t.tname='諶燕'
)

******************************************************************

16、向SC 表中插入一些記錄，這些記錄要求符合以下條件：沒有上過編號“c002”課程的同學學號、“c002”號課的平均成績；

insert into sc (sno,cno,score)
 select distinct st.sno,sc.cno,(select avg(score)from sc where cno='c002')
 from student st,sc
 where not exists
 (select * from sc where cno='c002' and sc.sno=st.sno) and sc.cno='c002';

******************************************************************

17、查詢各科成績最高和最低的分：以如下形式顯示：課程ID，最高分，最低分

select cno ,max(score),min(score) from sc group by cno;

******************************************************************

18、按各科平均成績從低到高和及格率的百分數從高到低順序

select cno,avg(score),sum(case when score>=60 then 1 else 0 end)/count(*) as 及格率
from sc group by cno
order by avg(score) , 及格率 desc

******************************************************************

19、查詢不同老師所教不同課程平均分從高到低顯示

select max(t.tno),max(t.tname),max(c.cno),max(c.cname),c.cno,avg(score) from sc , course c,teacher t
where sc.cno=c.cno and c.tno=t.tno
group by c.cno
order by avg(score) desc

******************************************************************

20、統計列印各科成績,各分數段人數:課程ID,課程名稱,[100-85],[85-70],[70-60],[ <60]

select sc.cno,c.cname,
sum(case  when score between 85 and 100 then 1 else 0 end) AS "[100-85]",
sum(case  when score between 70 and 85 then 1 else 0 end) AS "[85-70]",
sum(case  when score between 60 and 70 then 1 else 0 end) AS "[70-60]",
sum(case  when score <60 then 1 else 0 end) AS "[<60]"
from sc, course c
where  sc.cno=c.cno
group by sc.cno ,c.cname;

******************************************************************

21、查詢各科成績前三名的記錄:(不考慮成績並列情況)

select * from
(select sno,cno,score,row_number()over(partition by cno order by score desc) rn from sc)
where rn<4

******************************************************************

22、查詢每門課程被選修的學生數

select cno,count(sno)from sc group by cno;

******************************************************************

23、查詢出只選修了一門課程的全部學生的學號和姓名

select sc.sno,st.sname,count(cno) from student st
left join sc
on sc.sno=st.sno
group by st.sname,sc.sno having count(cno)=1;

******************************************************************

24、查詢男生、女生人數

select ssex,count(*)from student group by ssex;

******************************************************************

25、查詢姓“張”的學生名單

select * from student where sname like '張%';

******************************************************************

26、查詢同名同性學生名單，並統計同名人數

select sname,count(*)from student group by sname having count(*)>1;

******************************************************************

27、1981 年出生的學生名單(注：Student 表中Sage 列的類型是number)

select sno,sname,sage,ssex from student t where to_char(sysdate,'yyyy')-sage =1988

******************************************************************

28、查詢每門課程的平均成績，結果按平均成績升序排列，平均成績相同時，按課程號降序排列

select cno,avg(score) from sc group by cno order by avg(score)asc,cno desc;

******************************************************************

29、查詢平均成績大於85 的所有學生的學號、姓名和平均成績

select st.sno,st.sname,avg(score) from student st
left join sc on sc.sno=st.sno
group by st.sno,st.sname having avg(score)>85;

******************************************************************

30、查詢課程名稱為“數據庫”，且分數低於60 的學生姓名和分數

select sname,score from student st,sc,course c
where st.sno=sc.sno and sc.cno=c.cno and c.cname='Oracle' and sc.score<60

******************************************************************

31、查詢所有學生的選課情況；

select st.sno,st.sname,c.cname from student st,sc,course c
where sc.sno=st.sno and sc.cno=c.cno;

******************************************************************

32、查詢任何一門課程成績在70 分以上的姓名、課程名稱和分數；

select st.sname,c.cname,sc.score from student st,sc,course c
where sc.sno=st.sno and sc.cno=c.cno and sc.score>70

******************************************************************

33、查詢不及格的課程，並按課程號從大到小排列

select sc.sno,c.cname,sc.score from sc,course c
where sc.cno=c.cno and sc.score<60 order by sc.cno desc;

******************************************************************

34、查詢課程編號為c001 且課程成績在80 分以上的學生的學號和姓名；

select st.sno,st.sname,sc.score from sc,student st
where sc.sno=st.sno and cno='c001' and score>80;

******************************************************************

35、求選了課程的學生人數

select count(distinct sno) from sc;

******************************************************************

36、查詢選修“諶燕”老師所授課程的學生中，成績最高的學生姓名及其成績

select st.sname,score from student st,sc ,course c,teacher t
where
st.sno=sc.sno and sc.cno=c.cno and c.tno=t.tno and t.tname='諶燕' and sc.score=
(select max(score)from sc where sc.cno=c.cno)

******************************************************************

37、查詢各個課程及相應的選修人數

select cno,count(sno) from sc group by cno;

******************************************************************

38、查詢不同課程成績相同的學生的學號、課程號、學生成績

select a.* from sc a ,sc b where a.score=b.score and a.cno<>b.cno

******************************************************************

39、查詢每門功課成績最好的前兩名

select * from (
 select sno,cno,score,row_number()over(partition by cno order by score desc) my_rn from sc t
)
where my_rn<=2

******************************************************************

40、統計每門課程的學生選修人數（超過10 人的課程才統計）。要求輸出課程號和選修人數，查詢結果按人數降序排列，若人數相同，按課程號升序排列

select cno,count(sno) from sc 
group by cno having count(sno)>10
order by count(sno) desc,cno asc;

******************************************************************

41、檢索至少選修兩門課程的學生學號

select sno from sc group by sno having count(cno)>1;
或
select sno from sc group by sno having count(sno)>1;

******************************************************************

42、查詢全部學生都選修的課程的課程號和課程名

select distinct(c.cno),c.cname from course c ,sc where sc.cno=c.cno
或
select cno,cname from course c where c.cno in (select cno from sc group by cno)

******************************************************************

43、查詢沒學過“諶燕”老師講授的任一門課程的學生姓名

select st.sname from student st
where st.sno not in
(select distinct sc.sno from sc,course c,teacher t where sc.cno=c.cno and c.tno=t.tno and t.tname='諶燕')

******************************************************************

44、查詢兩門以上不及格課程的同學的學號及其平均成績

select sno,avg(score)from sc
where sno in
(
 select sno from sc where sc.score<60
 group by sno having count(sno)>1
) group by sno

******************************************************************

45、檢索“c004”課程分數小於60，按分數降序排列的同學學號

select sno from sc where cno='c004' and score<90 order by score desc;

******************************************************************

46、刪除“s002”同學的“c001”課程的成績

delete from sc where sno='s002' and cno='c001';