mysql操作表语句练习

1.表结构:

2.建表

# 1、创建表
# 创建班级表
create table class(
cid int primary key auto_increment,
caption varchar(32) not null
);

# 创建学生表
create table student(
sid int primary key auto_increment,
gender char(1) not null,
class_id int not null,
sname varchar(32) not null,
foreign key(class_id) references class(cid) on delete cascade on update cascade
);

# 创建老师表
create table teacher(
tid int primary key auto_increment,
tname varchar(32) not null
);

# 创建课程表
create table course(
cid int primary key auto_increment,
cname varchar(32) not null,
teacher_id int not null,
foreign key(teacher_id) references teacher(tid) on delete cascade on update cascade
);

# 创建成绩表
create table score(
sid int primary key auto_increment,
student_id int not null,
course_id int not null,
num int not null,
foreign key(student_id) references student(sid) on delete cascade on update cascade,
foreign key(course_id) references course(cid) on delete cascade on update cascade
);


# 2、插入记录
# 班级表插入记录
insert into class values
('1', '三年二班'), 
('2', '三年三班'), 
('3', '一年二班'), 
('4', '二年一班');

# 学生表插入记录
insert into student values
('1', '男', '1', '理解'), 
('2', '女', '1', '钢蛋'), 
('3', '男', '1', '张三'), 
('4', '男', '1', '张一'), 
('5', '女', '1', '张二'), 
('6', '男', '1', '张四'), 
('7', '女', '2', '铁锤'),
('8', '男', '2', '李三'), 
('9', '男', '2', '李一'), 
('10', '女', '2', '李二'), 
('11', '男', '2', '李四'), 
('12', '女', '3', '如花'), 
('13', '男', '3', '刘三'), 
('14', '男', '3', '刘一'), 
('15', '女', '3', '刘二'), 
('16', '男', '3', '刘四');

# 老师表插入记录
insert into teacher values
('1', '张磊'), 
('2', '李平'), 
('3', '刘海燕'), 
('4', '朱云海'), 
('5', '李春秋');

# 课程表插入记录
insert into course values
('1', '生物', '1'), 
('2', '物理', '2'), 
('3', '体育', '3'), 
('4', '美术', '2');

# 成绩表插入记录
insert into score values
('1', '1', '1', '10'), 
('2', '1', '2', '9'), 
('3', '1', '3', '76'),
('5', '1', '4', '66'), 
('6', '2', '1', '8'), 
('8', '2', '3', '68'), 
('9', '2', '4', '99'), 
('10', '3', '1', '77'), 
('11', '3', '2', '66'), 
('12', '3', '3', '87'), 
('13', '3', '4', '99'), 
('14', '4', '1', '79'), 
('15', '4', '2', '11'), 
('16', '4', '3', '67'), 
('17', '4', '4', '100'), 
('18', '5', '1', '79'), 
('19', '5', '2', '11'), 
('20', '5', '3', '67'), 
('21', '5', '4', '100'), 
('22', '6', '1', '9'), 
('23', '6', '2', '100'), 
('24', '6', '3', '67'), 
('25', '6', '4', '100'), 
('26', '7', '1', '9'), 
('27', '7', '2', '100'), 
('28', '7', '3', '67'), 
('29', '7', '4', '88'), 
('30', '8', '1', '9'), 
('31', '8', '2', '100'), 
('32', '8', '3', '67'),
('33', '8', '4', '88'), 
('34', '9', '1', '91'), 
('35', '9', '2', '88'), 
('36', '9', '3', '67'), 
('37', '9', '4', '22'), 
('38', '10', '1', '90'), 
('39', '10', '2', '77'), 
('40', '10', '3', '43'), 
('41', '10', '4', '87'), 
('42', '11', '1', '90'), 
('43', '11', '2', '77'), 
('44', '11', '3', '43'), 
('45', '11', '4', '87'), 
('46', '12', '1', '90'), 
('47', '12', '2', '77'), 
('48', '12', '3', '43'), 
('49', '12', '4', '87'), 
('52', '13', '3', '87');

3.练习题目

做题之前建议自己先在脑海中理出联表的关系结构，如：

student(主联) -> class (被联)
course(主联) -> teacher(被联)
score(主联) -> course, stundent(被联)

# 1、查询所有的课程的名称以及对应的任课老师姓名

# 分析：联表 course,teacher 进行查询

1.select co.cname, t.tname from course as co 
inner join teacher as t on co.teacher_id = t.tid
2.select co.cname, t.tname from course as co,
 teacher as t where co.teacher_id = t.tid

# 2、查询学生表中男女生各有多少人

1.select  gender,count(*) from student group by sex

# 3、查询物理成绩等于100的学生的姓名

分析:需要联三个表,score 是中间联系的表
1.select student.sname from score inner join student on course.cid = 
score.course_id inner join stundent on stundent.sid = score.student_id 

# 4、查询平均成绩大于八十分的同学的姓名和平均成绩

1.select student.sname, average(num) from student 
inner join score on student.sid = score.student_id 
group by student_id having avg(num )> 80

# 5、查询所有学生的学号，姓名，选课数，总成绩

select student_id, sname, count(*), sum(num) from score inner join student on score.student_id = student.sid group by student_id

# 6、 查询姓李老师的个数

select count(*) from teacher where tname like  "李%"

7、 查询没有报李平老师课的学生姓名

#第一步反向找到选了李老师课程的学生ID

#第二步通过ID找到没选李老师课程的ID

select sid, sname from student where sid not in

distinct(select stundent_id  from score, course, teacher 
where teacher.tid = course.teacher_id and 
course.cid = score.course_id and teacher.tname = "李平"   )

8、 查询物理课程的分数比生物课程的分数高的学生的学号

#1.分别选出所有学生物理/生物课程的分数表，

#2.将两表联表查询

select sid, sname from (

select  score.student_id as s1, num from score inner join student on 
course.cid  = score.course_id where course.cname = "物理"

) as t1 inner join (

select  score.student_id as s1,num from score inner join course on
 course.cid = score.course_id where course.cname = "生物"

) as t2 on t1.s1 = t2.s1 where t1.num > t2.num  

9、 查询没有同时选修物理课程和体育课程的学生姓名

#1.分别查询出选修了物理/体育课程的学生表

#2.联表查询出两个都选了的学生表

#3.通过上面的cid从student中反向查询出学生姓名

10、查询挂科超过两门(包括两门)的学生姓名和班级

select score.stundent_id, student.sname, class.caption from  score 
inner join stundent on score.student_id = student.sid  
inner join calss on student.class_id = class.cid  
group by student_id having count(*) >= 2

11、查询选修了所有课程的学生姓名

#1先算出所有课程的数目

#2按课程分组，找出课程数量等于1结果的课程id

select score.student_id, student.sname from score 
inner join stundent on score.student_id = stundent.sid 
group by stundent_id 
having count(*) = (select count( * ) from course  )

12、查询李平老师教的课程的所有成绩记录

#查询李平老师教的所有课程id

#从score表中查找所有课程的成绩记录

13、查询全部学生都选修了的课程号和课程名

#求出所有学生的数量

#score按course_id 分组，计算出 count(*) = 1中结果

14、查询每门课程被选修的次数

select course_id, count(*) from score group by course_id 

15、查询只选修了一门课程的学生学号和姓名

#course和student联表，按stundent_id 分组，count(*)=1

select score.student_id, student.sname from score 
inner join student on score.student_id = student.sid 
group by student_id having count(*) = 1

16、查询所有学生考出的成绩并按从高到低排序（成绩去重）

#去重，排序

select diatinct num from  score order by num desc

17、查询平均成绩大于85的学生姓名和平均成绩

#联表score和student，按stundent_id分组，平均成绩大于85

select score.student_id, student.sname, avg(num) from score 
inner join student on score.student_id = student.sid 
group by student_id having avg(num) > 85

18、查询生物成绩不及格的学生姓名和对应生物分数

#联表，加条件

select student.sname, score.num from score 
inner join student on score.student_id = student.sid inner j
oin course on score.course_id = course.sid 
where course.cname = "生物" and num > 85

19、查询在所有选修了李平老师课程的学生中，这些课程(李平老师的课程，不是所有课程)平均成绩最高的学生姓名



20、查询每门课程成绩最好的课程id、学生姓名和分数

21、查询不同课程但成绩相同的课程号、学生号、成绩


22、查询没学过“李平”老师课程的学生姓名以及选修的课程名称


23、查询所有选修了学号为2的同学选修过的一门或者多门课程的同学学号和姓名 24、任课最多的老师中学生单科成绩最高的课程id、学生姓名和分数