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

為sc表中的sno和cno創建外鍵

alter table sc add foreign key(sno) references student(sno);

alter table sc add foreign key(cno) references course(cno);

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

a) 插入如下學生記錄(學號：95030，姓名：李莉，年齡：18)

insert into student(sno,sname,sage) values('95030','李莉',18);

b) 插入如下選課記錄(95030，1)

insert int sc(sno,cno) values('95030','001');

c) 計算機系學生年齡改成20

update student set sage = 20 where sdept = 'cs';

d) 數學系所有學生成績改成0

update sc set grade = 0 where cno = '002';

e) 把低于總平均成績的女同學成績提高5分

f) 修改2號課程的成績，若成績小于75分提高5％，成績大于75時提高

4％(兩個語句實現，注意順序)

update sc set grade=grade+grade*0.05 where cno='002' and grade<75;

update sc set grade=grade+grade*0.04 where cno='002' and grade>75;

g) 刪除95030學生信息

delete from student where sno = '95030';

h) 刪除SC表中無成績的記錄

delete from sc where grade is null;

i) 刪除張娜的選課記錄

delete from sc where sno = (select sno from student where sname = '張娜');

j) 刪除數學系所有學生選課記錄

delete from sc where cno = '002';

k) 刪除不及格的學生選課記錄

delete from sc where grade < 60;

l) 查詢每一門課程成績都大于等于80分的學生學號、姓名和性別，把值送往另一個已經存在的基本表STU(SNO,SNAME,SSEX)中

insert into stu(sno,sname,ssex)

select student.sno,student.sname,student.ssex

from student,sc

where student.sno=sc.sno and sc.grade>=80;

m) 把所有學生學號和課程號連接追加到新表中

insert into STUsc(sno,cno)

select student.sno,sc.cno from student,sc

where student.sno = sc.sno;

n) 所有學生年齡增1

update student set sage = sage+1;

o) 統計3門以上課程不及格的學生把

相應的學生姓名、系別追加到另外一個表中

insert into stu(sname,sdept) --插入表中

select sname,sdept from student,sc --選擇出列名

where --條件

student.sno=(select sno from sc

where grade<60 group by sno having count(*)>3);

查詢每個學生及其選課情況；

select sno,cno from sc;

將STUDENT,SC進行右連接

查詢有不及格的學生姓名和所在系

select a.sname,a.sdept from student a right join sc b on a.sno = b.sno;

查詢所有成績為優秀(大于90分)的學生姓名

select a.grade,b.sname ,a.sno

from sc a right join student b on a.grade > 90 and a.sno = b.sno;

+-------+--------+-------+

| grade | sname | sno |

+-------+--------+-------+

| NULL | 麗麗 | NULL |

| NULL | 趙海 | NULL |

| 97 | 劉晨 | 08005 |

| 93 | 劉丹丹 | 08006 |

| NULL | 劉立 | NULL |

| NULL | 王江 | NULL |

| NULL | 高曉 | NULL |

| 100 | 張麗 | 08010 |

| NULL | NULL | NULL |

+-------+--------+-------+

select a.grade,b.sname ,a.sno from sc a

join student b on a.grade > 90 and a.sno = b.sno;

+-------+--------+-------+

| grade | sname | sno |

+-------+--------+-------+

| 97 | 劉晨 | 08005 |

| 93 | 劉丹丹 | 08006 |

| 100 | 張麗 | 08010 |

+-------+--------+-------+

查詢既選修了2號課程又選修了3號課程的

學生姓名、學號；

select sname,sno from student where sno in(

select sno from sc

where cno = '003'

and

sno in(select sno from sc where cno = '006'));

----或者

select a.sname,a.sno from student a join sc b where a.sno = b.sno and cno = '003' and b.sno in(select sno from sc where cno = '006');

查詢和劉晨同一年齡的學生

select sno ,sname from student where sage = (select sage from student where sname = '劉晨');

選修了課程名為“數據庫”的學生姓名和年齡

select a.sname,a.sage from student a join sc b on a.sno = b.sno and b.cno = '001

查詢其他系比IS系任一學生年齡小的學生名單

select sname,sage from student where sage < any

(select sage from student where sdept = 'is');

查詢其他系中比IS系所有學生年齡都小的學生名單

select sname,sage from student where sage < all

(select sage from student where sdept = 'is');

查詢選修了全部課程的學生姓名

select sname,sno

from student where sno in(select sno from sc);

查詢計算機系學生及其性別是男的學生

select *from student where sdept = 'cs' and ssex = '男';

查詢選修課程1的學生集合和選修2號課程學生集合的差集

select sno from sc where cno = '001' and sno not

in(select sno from sc where cno = '002');

查詢李麗同學不學的課程的課程號

select cno from course where cno not in(select a.cno from sc a join student b on a.sno = b.sno and b.sname = '李麗');

查詢選修了3號課程的學生平均年齡

select avg(sage) from student where sno in(select sno from sc where cno = '003');

求每門課程學生的平均成績

select avg(grade) from sc group by cno;

統計每門課程的學生選修人數(超過3人的才統計)。要求輸出課程號和選修人數，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(*) from sc group by cno having count(sno) > 3;

查詢學號比劉晨大，而年齡比他小的學生姓名。

select sname from student where

sno > (select sno from student where sname = '劉晨')

and sage < (select sage from student where sname = '劉晨')；

求年齡大于女同學平均年齡的男同學姓名和年齡

select sname,sage from student where ssex = '男' and

sage > (select avg(sage) from student where ssex = '女');

求年齡大于所有女同學年齡的男同學姓名和年齡

select sname,sage from student where ssex = '男' and

sage > all (select sage from student where ssex = '女');

查詢95001和95002兩個學生都選修的課程的信息

select *from sc where sno in ('95001','95002');

-----------------------------------------------------

alter table student add test varchar(20); -

alter table student drop test; -

-----------------------------------------------------

為學生表按學號建立唯一索引

mysql> create UNIQUE INDEX stusno ON student(sno);

Query OK, 10 rows affected (0.61 sec)

Records: 10 Duplicates: 0 Warnings: 0

為course表按課程號升序(默認)建立唯一索引

mysql> create UNIQUE INDEX coucno ON course(cno);

Query OK, 7 rows affected (0.38 sec)

Records: 7 Duplicates: 0 Warnings: 0

為sc表按學號升序和課程號降序建立唯一索引

mysql> create UNIQUE INDEX scno ON sc(sno asc,cno desc);

Query OK, 11 rows affected (0.34 sec)

Records: 11 Duplicates: 0 Warnings: 0

//刪除索引

drop index scno on sc;

//插入學生信息

insert into student (sno,sname,sage) values('95030','；李莉',18);

a) 查詢全體學生的學號和姓名

select sno,sname from student;

b) 查詢全體學生的詳細記錄

select *from student;

c) 查詢所有選修過課程的學生學號

select distinct sno from sc ;

d) 查詢考試有不及格的學生學號

select sno from sc where grade < 60;

e) 查詢不是信息系(IS)、計算機系(CS)的學生性別、年齡、系別

select sname,ssex,sdept from student where sdept not in('is','cs');

f) 查詢選修了4號課的學生學號和成績，結果按成績降序排列

select sno,grade from sc where cno = '004' order by grade desc;

g) 查詢每個課程號和相應的選課人數

select cno,count(cno) as cnonumed from sc group by cno;

h) 查詢計算機系(CS)的學生姓名、年齡、系別

select sname,sage,sdept from student where sdept = 'cs';

i) 查詢年齡18－20歲的學生學號、姓名、系別、年齡；

select sname,sage,sdept from student where sage between 18 and 20;

j) 查詢姓劉的學生情況

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

k) 查詢既選修3號課程，又選修6號課程的學生學號和成績

select sno ,grade from sc

where cno = '003'

and

sno in(select sno from sc where cno = '006');

l) 查詢學生的姓名和出生年份(今年2003年)

select sname,sbirthday from student;

m) 查詢沒有成績的學生學號和課程號

select sno,cno from sc where grade is null;

n) 查詢總成績大于200分的學生學號

select sno,sum(grade) from sc

group by sno having sum(grade) > 200;

o) 查詢每門課程不及格學生人數

select cno,count(sno) from sc

where grade < 90

group by cno;

p) 查詢不及格課程超過3門的學生學號

select cno,count(sno) from sc

where grade < 60

group by cno

having count(sno) > 3;

q) 查詢年齡在10到19歲之間的學生信息

select *from student

where sage between 10 and 19;

r) 查詢全體學生情況，按所在系升序排列，同一個系的學生按年齡降序排列

select *from student order by sdept asc,sage desc;

s) 查詢選了1號課程的學生平均成績

select cno,avg(grade) from sc where cno = '001' group by cno;

+-----+------------+

| cno | avg(grade) |

+-----+------------+

| 001 | 92.6667 |

+-----+------------+

1 row in set (0.00 sec)

mysql> select cno,avg(grade) from sc group by cno having cno = '001';

+-----+------------+

| cno | avg(grade) |

+-----+------------+

| 001 | 92.6667 |

+-----+------------+

t) 查詢選了3號課程的學生的最高分

select cno, max(grade)

from sc where cno = '003' group by cno;

u) 查詢每個同學的總成績

select sno,sum(grade)

from sc

group by sno;

總結

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