MySQL练手小试题
创建表和数据
创建class表
create table class (
cid int(11) primary key auto_increment,
caption varchar(32) not null
);
insert into class(caption) values("三年二班"),("三年三班"),("一年二班"),("二年九班");
select * from class;
+-----+--------------+
| cid | caption |
+-----+--------------+
| 1 | 三年二班 |
| 2 | 三年三班 |
| 3 | 一年二班 |
| 4 | 二年九班 |
+-----+--------------+
创建学生表
create table student(
sid int(11) primary key auto_increment,
gender char(1) not null,
class_id int(11) not null,
sname varchar(32) not null,
foreign key(class_id) references class(cid)
);
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');
select * from student;
+-----+--------+----------+--------+
| sid | gender | class_id | sname |
+-----+--------+----------+--------+
| 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 |
+-----+--------+----------+--------+
创建老师表
create table teacher(
tid int(11) primary key auto_increment,
tname varchar(32) not null
);
insert into teacher values('1', '张磊老师'), ('2', '李平老师'), ('3', '刘海燕老师'), ('4', '朱云海老师'), ('5', '李杰老师');
select * from teacher;
+-----+-----------------+
| tid | tname |
+-----+-----------------+
| 1 | 张磊老师 |
| 2 | 李平老师 |
| 3 | 刘海燕老师 |
| 4 | 朱云海老师 |
| 5 | 李杰老师 |
+-----+-----------------+
创建课程表
create table course(
cid int(11) primary key auto_increment,
cname varchar(32) not null,
teacher_id int(11) not null,
foreign key(teacher_id) references teacher(tid)
);
insert into course values('1', '生物', '1'), ('2', '物理', '2'), ('3', '体育', '3'), ('4', '美术', '2');
select * from course;
+-----+--------+------------+
| cid | cname | teacher_id |
+-----+--------+------------+
| 1 | 生物 | 1 |
| 2 | 物理 | 2 |
| 3 | 体育 | 3 |
| 4 | 美术 | 2 |
+-----+--------+------------+
创建成绩表
create table score(
sid int(11) primary key auto_increment,
student_id int(11) not null,
course_id int(11) not null,
num int(11) not null,
foreign key(student_id) references student(sid),
foreign key(course_id) references course(cid)
);
insert into score values('1', '1', '1', '10'), ('2', '1', '2', '9'), ('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');
select * from score;
+-----+------------+-----------+-----+
| sid | student_id | course_id | num |
+-----+------------+-----------+-----+
| 1 | 1 | 1 | 10 |
| 2 | 1 | 2 | 9 |
| 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 |
+-----+------------+-----------+-----+
题目
查询所有的课程的名称以及对应的任课老师姓名
mysql> select cid,cname,tname from course left join teacher on teacher_id = tid order by cid; +-----+--------+-----------------+
| cid | cname | tname |
+-----+--------+-----------------+
| 1 | 生物 | 张磊老师 |
| 2 | 物理 | 李平老师 |
| 3 | 体育 | 刘海燕老师 |
| 4 | 美术 | 李平老师 |
+-----+--------+-----------------+
查询学生表中男女生各有多少人
mysql> select gender,count(*) as total from student group by gender;
+--------+-------+
| gender | total |
+--------+-------+
| 女 | 6 |
| 男 | 10 |
+--------+-------+
查询物理成绩等于100的学生的姓名
select sname from student join score join course
on
student.sid = student_id and course_id = course.cid
where cname = "物理" and num = 100;
+--------+
| sname |
+--------+
| 张四 |
| 铁锤 |
| 李三 |
+--------+
查询平均成绩大于八十分的同学的姓名和平均成绩
select sname,sum(num)/4 average_score from student join score
on student_id = student.sid group by sname
having sum(num)/4 > 80;
+--------+---------------+
| sname | average_score |
+--------+---------------+
| 张三 | 82.2500 |
+--------+---------------+
查询所有学生的学号，姓名，选课数，总成绩
select student.sid as sid,sname,count(*) count_course,sum(num) summary from student left join score on student_id = student.sid group by sname order by student.sid;
+-----+--------+--------------+---------+
| sid | sname | count_course | summary |
+-----+--------+--------------+---------+
| 1 | 理解 | 3 | 85 |
| 2 | 钢蛋 | 3 | 175 |
| 3 | 张三 | 4 | 329 |
| 4 | 张一 | 4 | 257 |
| 5 | 张二 | 4 | 257 |
| 6 | 张四 | 4 | 276 |
| 7 | 铁锤 | 4 | 264 |
| 8 | 李三 | 4 | 264 |
| 9 | 李一 | 4 | 268 |
| 10 | 李二 | 4 | 297 |
| 11 | 李四 | 4 | 297 |
| 12 | 如花 | 4 | 297 |
| 13 | 刘三 | 1 | 87 |
| 14 | 刘一 | 1 | NULL |
| 15 | 刘二 | 1 | NULL |
| 16 | 刘四 | 1 | NULL |
+-----+--------+--------------+---------+
查询姓李老师的个数
select group_concat(tname) tname,count(*) count from teacher where tname like "李%";
+---------------------------+-------+
| tname | count |
+---------------------------+-------+
| 李平老师,李杰老师 | 2 |
+---------------------------+-------+
查询没有报李平老师课的学生姓名
select sname from student where sid not in (
select student_id from score where course_id in (
select cid from course where teacher_id in (
select tid from teacher where tname = "李平老师"
)
)
);
+--------+
| sname |
+--------+
| 刘三 |
| 刘一 |
| 刘二 |
| 刘四 |
+--------+
查询物理课程比生物课程高的学生的学号
select t1.student_id from( (select * from score where course_id in (select cid from course where cname = '生物')) t1 left join (select * from score where course_id in (select cid from course where cname = '物理')) t2 on t1.student_id = t2.student_id) where t1.num < t2.num; +------------+
| student_id |
+------------+
| 6 |
| 7 |
| 8 |
+------------+
查询没有同时选修物理课程和体育课程的学生姓名
select sname from student where sid not in (
select student_id from score where course_id in (
select cid from course where cname in ("物理","体育")
) group by student_id having count(*) = 2
); +--------+
| sname |
+--------+
| 理解 |
| 钢蛋 |
| 刘三 |
| 刘一 |
| 刘二 |
| 刘四 |
+--------+
查询挂科超过两门(包括两门)的学生姓名和班级
select sname,caption from student join class on cid = class_id
where sid=(select student_id from score where num < 60 group by student_id having count(*) >= 2);
+--------+--------------+
| sname | caption |
+--------+--------------+
| 理解 | 三年二班 |
+--------+--------------+
查询选修了所有课程的学生姓名
select sname from student where sid in (
select student_id from score group by student_id having count(*) = 4
);
+--------+
| sname |
+--------+
| 张三 |
| 张一 |
| 张二 |
| 张四 |
| 铁锤 |
| 李三 |
| 李一 |
| 李二 |
| 李四 |
| 如花 |
+--------+
查询李平老师教的课程的所有成绩记录
select num from score where course_id in (
select cid from course where teacher_id = (
select tid from teacher where tname = "李平老师"
)
);
+-----+
| num |
+-----+
| 9 |
| 66 |
| 11 |
| 11 |
| 100 |
| 100 |
| 100 |
| 88 |
| 77 |
| 77 |
| 77 |
| 66 |
| 99 |
| 99 |
| 100 |
| 100 |
| 100 |
| 88 |
| 88 |
| 22 |
| 87 |
| 87 |
| 87 |
+-----+
查询全部学生都选修了的课程号和课程名
select cid,cname from course where cid in(
select course_id from score group by course_id having count(*) = 4
);
Empty set (0.00 sec)
查询每门课程被选修的次数
select cname,count(*) from course join score on cid = course_id group by course_id;
+--------+----------+
| cname | count(*) |
+--------+----------+
| 生物 | 12 |
| 物理 | 11 |
| 体育 | 12 |
| 美术 | 12 |
+--------+----------+
查询之选修了一门课程的学生姓名和学号
select sname,sid from student where sid in(
select student_id from score group by student_id having count(*) = 1
);
+--------+-----+
| sname | sid |
+--------+-----+
| 刘三 | 13 |
+--------+-----+
查询所有学生考出的成绩并按从高到低排序（成绩去重）
select distinct num from score order by num desc;
+-----+
| num |
+-----+
| 100 |
| 99 |
| 91 |
| 90 |
| 88 |
| 87 |
| 79 |
| 77 |
| 68 |
| 67 |
| 66 |
| 43 |
| 22 |
| 11 |
| 10 |
| 9 |
| 8 |
+-----+
查询平均成绩大于85的学生姓名和平均成绩
select sname,avg(num) average_score from student join score
on student_id = student.sid group by sname
having avg(num) > 85;
+--------+---------------+
| sname | average_score |
+--------+---------------+
| 刘三 | 87.0000 |
+--------+---------------+
查询生物成绩不及格的学生姓名和对应生物分数
select sname,num from student join score on student.sid = student_id
where num < 60 and course_id = (
select cid from course where cname = "生物"
);
+--------+-----+
| sname | num |
+--------+-----+
| 理解 | 10 |
| 钢蛋 | 8 |
| 张四 | 9 |
| 铁锤 | 9 |
| 李三 | 9 |
+--------+-----+
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
select sname,avg(num) from student join score join course join teacher on
student.sid = student_id and course.cid = course_id and teacher_id = tid where
tname = "李平老师" group by student_id order by avg(num) desc limit 1; +--------+----------+
| sname | avg(num) |
+--------+----------+
| 张四 | 100.0000 |
+--------+----------+
查询每门课程成绩最好的前两名学生姓名
(select cname,sname from course join score join student
on course_id = course.cid and student.sid = student_id
where cname = "生物" order by num desc limit 2)
union
(select cname,sname from course join score join student
on course_id = course.cid and student.sid = student_id
where cname = "物理" order by num desc limit 2)
union
(select cname,sname from course join score join student
on course_id = course.cid and student.sid = student_id
where cname = "美术" order by num desc limit 2)
union
(select cname,sname from course join score join student
on course_id = course.cid and student.sid = student_id
where cname = "体育" order by num desc limit 2) +--------+--------+
| cname | sname |
+--------+--------+
| 生物 | 李一 |
| 生物 | 如花 |
| 物理 | 李三 |
| 物理 | 铁锤 |
| 美术 | 张四 |
| 美术 | 张二 |
| 体育 | 刘三 |
| 体育 | 张三 |
+--------+--------+
查询不同课程但成绩相同的学号，课程号，成绩
select distinct s1.course_id,s2.course_id,s1.num,s2.num from score as s1, score as s2 where s1.num = s2.num and s1.course_id != s2.course_id; +-----------+-----------+-----+-----+
| course_id | course_id | num | num |
+-----------+-----------+-----+-----+
| 1 | 2 | 9 | 9 |
| 2 | 4 | 66 | 66 |
| 2 | 1 | 77 | 77 |
| 4 | 2 | 66 | 66 |
| 4 | 3 | 87 | 87 |
| 2 | 4 | 100 | 100 |
| 2 | 1 | 9 | 9 |
| 4 | 2 | 100 | 100 |
| 2 | 4 | 88 | 88 |
| 4 | 2 | 88 | 88 |
| 1 | 2 | 77 | 77 |
| 3 | 4 | 87 | 87 |
+-----------+-----------+-----+-----+
查询没学过“叶平”老师课程的学生姓名以及选修的课程名称；
select sname,cname from student join score join course on
student.sid = student_id and course.cid = course_id
where student.sid not in (
select distinct student_id from score where course_id in(
select cid from course where teacher_id in (
select tid from teacher where tname = "李平老师"
)
)
); +--------+--------+
| sname | cname |
+--------+--------+
| 刘三 | 体育 |
+--------+--------+
查询所有选修了学号为1的同学选修过的一门或者多门课程的同学学号和姓名；
select sid,sname from student where sid in (
select student_id from score where course_id in(
select course_id from score where student_id = 1
)
); +-----+--------+
| sid | sname |
+-----+--------+
| 1 | 理解 |
| 2 | 钢蛋 |
| 3 | 张三 |
| 4 | 张一 |
| 5 | 张二 |
| 6 | 张四 |
| 7 | 铁锤 |
| 8 | 李三 |
| 9 | 李一 |
| 10 | 李二 |
| 11 | 李四 |
| 12 | 如花 |
+-----+--------+
任课最多的老师中学生单科成绩最高的学生姓名
select sname from student join score join course on student_id = student.sid and course_id = cid where teacher_id = (
select teacher_id from (select teacher_id,count(*) as total from course group by teacher_id order by total desc limit 1) as t
)
group by course_id having max(num);
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