mysql-作业
一、表关系
请创建如下表,并创建相关约束
班级表:class | 学生表:student | ||||||
cid | caption | grade_id | sid | sname | gender | class_id | |
1 | 一年一班 | 1 | 1 | 乔丹 | 女 | 1 | |
2 | 二年一班 | 2 | 2 | 艾弗森 | 女 | 1 | |
3 | 三年二班 | 3 | 3 | 科比 | 男 | 2 | |
老师表:teacher | 课程表:course | ||||||
tid | tname | cid | cname | teacher_id | |||
1 | 张三 | 1 | 生物 | 1 | |||
2 | 李四 | 2 | 体育 | 1 | |||
3 | 王五 | 3 | 物理 | 2 | |||
成绩表:score | 年级表:class_grade | ||||||
sid | student_id | course_id | score | gid | gname | ||
1 | 1 | 1 | 60 | 1 | 一年级 | ||
2 | 1 | 2 | 59 | 2 | 二年级 | ||
3 | 2 | 2 | 99 | 3 | 三年级 | ||
班级任职表:teach2cls | |||||||
tcid | tid | cid | |||||
1 | 1 | 1 | |||||
2 | 1 | 2 | |||||
3 | 2 | 1 | |||||
4 | 3 | 2 |
二、操作表
- -- 1、自行创建测试数据;
- create database db5;
- use db5;
- create table teacher (
- tid int primary key auto_increment,
- tname char(20) not null
- );
- insert into teacher(tname) values
- ('张三'),
- ('李四'),
- ('王五'),
- ('赵六'),
- ('马七');
- create table class_grade (
- gid int primary key auto_increment,
- gname char(20) not null
- );
- insert into class_grade(gname) values
- ('一年级'),
- ('二年级'),
- ('三年级'),
- ('四年级'),
- ('五年级');
- create table course (
- cid int primary key auto_increment,
- cname char(20) not null,
- teacher_id int,
- foreign key(teacher_id) references teacher(tid)
- on delete cascade
- on update cascade
- );
- insert into course(cname, teacher_id) values
- ('生物',1),
- ('体育',1),
- ('物理',2),
- ('语文',3),
- ('数学',4),
- ('外语',5);
- create table class (
- cid int primary key auto_increment,
- caption char(20),
- grade_id int,
- foreign key(grade_id) references class_grade(gid)
- on delete cascade
- on update cascade
- );
- insert into class(caption, grade_id) values
- ('一年一班',1),
- ('一年二班',1),
- ('二年一班',2),
- ('二年二班',2),
- ('三年一班',3),
- ('四年一班',4),
- ('五年一班',5);
- create table student (
- sid int primary key auto_increment,
- sname char(20),
- gender enum('男', '女') not null,
- class_id int,
- foreign key(class_id) references class(cid)
- on delete cascade
- on update cascade
- );
- insert into student(sname,gender,class_id) values
- ('乔丹','女',1),
- ('艾弗森','女',1),
- ('科比','男',2),
- ('curry','男',2),
- ('james','男',3),
- ('李瑞','女',4),
- ('白雪','女',5),
- ('无敌','男',5),
- ('天剑','男',6),
- ('egon','女',7),
- ('alex','男',7);
- create table score (
- sid int primary key auto_increment,
- student_id int,
- course_id int,
- score int,
- 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
- );
- insert into score(student_id, course_id, score) values
- (1,1,60),
- (1,2,59),
- (1,3,58),
- (1,4,71),
- (1,5,68),
- (1,6,100),
- (2,1,90),
- (2,2,99),
- (2,3,71),
- (2,4,68),
- (2,5,92),
- (2,6,88),
- (3,1,23),
- (3,2,55),
- (3,3,72),
- (3,4,88),
- (3,5,92),
- (3,6,12),
- (4,2,65),
- (4,4,78),
- (4,5,34),
- (5,2,75),
- (5,4,38),
- (5,5,44),
- (6,2,23),
- (6,4,32),
- (6,5,0),
- (7,1,78),
- (7,3,60),
- (7,6,45),
- (8,1,43),
- (8,3,65),
- (8,6,99),
- (9,2,56),
- (9,3,69),
- (9,5,78),
- (10,2,43),
- (10,3,69),
- (10,5,90),
- (11,2,90),
- (11,3,89),
- (11,5,100);
- create table teach2cls (
- tcid int primary key auto_increment,
- tid int,
- cid int,
- foreign key(tid) references teacher(tid)
- on delete cascade
- on update cascade,
- foreign key(cid) references class(cid)
- on delete cascade
- on update cascade
- );
- insert into teach2cls(tid, cid) values # 五个老师、七个班级
- (1,1),
- (1,2),
- (1,5),
- (1,7),
- (2,2),
- (2,3),
- (2,4),
- (2,6),
- (3,1),
- (3,2),
- (3,4),
- (3,5),
- (3,6),
- (4,2),
- (4,4),
- (4,7),
- (5,5),
- (5,6),
- (5,7);
- -- 2、查询学生总人数;
- select count(sid) as total_num from student;
- +-----------+
- | total_num |
- +-----------+
- | 11 |
- +-----------+
- -- 3、查询“生物”课程和“物理”课程成绩都及格的学生id和姓名;
- select sid, sname from student where sid in (
- select
- score.student_id # 先找到学习了这两们课且都及格学生的id
- from
- score
- inner join course
- on score.course_id=course.cid
- where
- course.cname in (
- '生物',
- '物理'
- )
- and score.score >=60
- group by
- score.student_id
- having
- count(course_id) =2
- );
- +-----+-----------+
- | sid | sname |
- +-----+-----------+
- | 2 | 艾弗森 |
- | 7 | 白雪 |
- +-----+-----------+
- -- 4、查询每个年级的班级数,取出班级数最多的前三个年级;
- select
- gname,count(class.cid)
- from
- class_grade
- inner join
- class
- on class.grade_id=class_grade.gid
- group by gid
- order by count(cid) DESC
- limit 3;
- +-----------+------------------+
- | gname | count(class.cid) |
- +-----------+------------------+
- | 一年级 | 2 |
- | 二年级 | 2 |
- | 四年级 | 1 |
- +-----------+------------------+
- -- 5、查询平均成绩最高和最低的学生的id和姓名以及平均成绩;
- select * from (
- select
- avg(score) as avg_score
- from
- score
- group by
- student_id
- order by avg_score ASC
- limit 1 ) t1 union
- select * from
- (select
- avg(score) as avg_score
- from
- score
- group by
- student_id
- order by avg_score DESC
- limit 1) t2;
- +-----------+
- | avg_score |
- +-----------+
- | 18.3333 |
- | 93.0000 |
- +-----------+
- select
- student_id,
- concat(student.sname) as student_name,
- avg(score)
- from
- student
- inner join
- score
- on score.student_id=student.sid
- group by
- student_id
- having
- avg(score) in (
- select * from (
- select
- avg(score) as avg_score
- from
- score
- group by
- student_id
- order by avg_score ASC
- limit 1 ) t1
- union
- select * from(
- select
- avg(score) as avg_score
- from
- score
- group by
- student_id
- order by avg_score DESC
- limit 1) t2
- );
- # 由于最小成绩是无限小数,无法显示
- +------------+--------------+------------+
- | student_id | student_name | avg(score) |
- +------------+--------------+------------+
- | 11 | alex | 93.0000 |
- +------------+--------------+------------+
- -- 6、查询每个年级的学生人数;
- select
- grade_id, count(sid)
- from
- student
- left join
- class
- on student.class_id=class.cid
- group by
- grade_id;
- +----------+------------+
- | grade_id | count(sid) |
- +----------+------------+
- | 1 | 4 |
- | 2 | 2 |
- | 3 | 2 |
- | 4 | 1 |
- | 5 | 2 |
- +----------+------------+
- select
- gname, t1.stu_num as stu_num
- from
- class_grade
- inner join
- (select
- grade_id, count(sid) as stu_num
- from
- student
- left join
- class
- on student.class_id=class.cid
- group by
- grade_id) as t1
- on class_grade.gid=t1.grade_id;
- +-----------+---------+
- | gname | stu_num |
- +-----------+---------+
- | 一年级 | 4 |
- | 二年级 | 2 |
- | 三年级 | 2 |
- | 四年级 | 1 |
- | 五年级 | 2 |
- +-----------+---------+
- -- 7、查询每位学生的学号,姓名,选课数,平均成绩;
- select
- student.sid,
- concat(student.sname),
- count(course_id) as course_num,
- avg(score) as avg_score
- from
- student
- inner join
- score
- on student.sid=score.student_id
- group by student.sid;
- +-----+-----------------------+------------+-----------+
- | sid | concat(student.sname) | course_num | avg_score |
- +-----+-----------------------+------------+-----------+
- | 1 | 乔丹 | 6 | 69.3333 |
- | 2 | 艾弗森 | 6 | 84.6667 |
- | 3 | 科比 | 6 | 57.0000 |
- | 4 | curry | 3 | 59.0000 |
- | 5 | james | 3 | 52.3333 |
- | 6 | 李瑞 | 3 | 18.3333 |
- | 7 | 白雪 | 3 | 61.0000 |
- | 8 | 无敌 | 3 | 69.0000 |
- | 9 | 天剑 | 3 | 67.6667 |
- | 10 | egon | 3 | 67.3333 |
- | 11 | alex | 3 | 93.0000 |
- +-----+-----------------------+------------+-----------+
- -- 8、查询学生编号为“2”的学生的姓名、该学生成绩最高的课程名、成绩最低的课程名及分数;
- # score——》student——》course
- select
- student.sname,
- course.cname,
- score.score
- from
- score
- left join student on score.student_id=student.sid
- left join course on score.course_id=course.cid
- where student.sid=2
- and score in (
- select * from (
- select
- max(score)
- from
- score
- where
- student_id=2) t1
- union
- select * from (
- select
- min(score)
- from
- score
- where
- student_id=2) t2
- );
- +-----------+--------+-------+
- | sname | cname | score |
- +-----------+--------+-------+
- | 艾弗森 | 体育 | 99 |
- | 艾弗森 | 语文 | 68 |
- +-----------+--------+-------+
- -- 9、查询姓“李”的老师的个数和所带班级数;
- select
- concat(teacher.tname),
- count(distinct teacher.tid) as teacher_num,
- count(teach2cls.cid) as class_num
- from
- teacher
- inner join
- teach2cls
- on teacher.tid=teach2cls.tid
- where
- tname like '李%'
- group by teacher.tid;
- +-----------------------+-------------+-----------+
- | concat(teacher.tname) | teacher_num | class_num |
- +-----------------------+-------------+-----------+
- | 李四 | 1 | 4 |
- +-----------------------+-------------+-----------+
- -- 10、查询班级数小于5的年级id和年级名;
- select
- gid,
- gname
- from
- class_grade
- where gid in (
- select
- grade_id
- from
- class
- group by
- grade_id
- having
- count(cid) < 5 )
- ;
- +-----+-----------+
- | gid | gname |
- +-----+-----------+
- | 1 | 一年级 |
- | 2 | 二年级 |
- | 3 | 三年级 |
- | 4 | 四年级 |
- | 5 | 五年级 |
- +-----+-----------+
- -- 11、查询班级信息,包括班级id、班级名称、年级、年级级别(12为低年级,34为中年级,56为高年级),示例结果如下;
- # mysql中case when then else end的用法
- select
- class.cid,
- class.caption,
- class_grade.gname,
- case # 如果
- when class_grade.gid between 1 and 2 then '低年级' # when后接条件,then后接返回值
- when class_grade.gid between 3 and 4 then '中年级'
- when class_grade.gid between 5 and 6 then '高年级'
- else 0 # 其他的返回值
- end as '年级级别' # end代表结束,自定义为'年级级别'
- from
- class
- inner join
- class_grade
- on class.grade_id=class_grade.gid;
- +-----+--------------+-----------+--------------+
- | cid | caption | gname | 年级级别 |
- +-----+--------------+-----------+--------------+
- | 1 | 一年一班 | 一年级 | 低年级 |
- | 2 | 一年二班 | 一年级 | 低年级 |
- | 3 | 二年一班 | 二年级 | 低年级 |
- | 4 | 二年二班 | 二年级 | 低年级 |
- | 5 | 三年一班 | 三年级 | 中年级 |
- | 6 | 四年一班 | 四年级 | 中年级 |
- | 7 | 五年一班 | 五年级 | 高年级 |
- +-----+--------------+-----------+--------------+
- -- 12、查询学过“张三”老师2门课以上的同学的学号、姓名;
- select
- sid,
- sname
- from
- student
- where
- sid in (
- select
- student_id
- from
- score
- where course_id in (
- select
- cid
- from
- course
- where
- teacher_id=(
- select
- tid
- from
- teacher
- where
- tname='张三'
- )
- )
- group by student_id
- having count(course_id)>=2
- );
- +-----+-----------+
- | sid | sname |
- +-----+-----------+
- | 1 | 乔丹 |
- | 2 | 艾弗森 |
- | 3 | 科比 |
- +-----+-----------+
- -- 13、查询教授课程超过2门的老师的id和姓名;
- select
- tid,
- tname
- from
- teacher
- where tid in (
- select
- teacher_id
- from
- course
- group by
- teacher_id
- having
- count(cid) >= 2
- );
- +-----+--------+
- | tid | tname |
- +-----+--------+
- | 1 | 张三 |
- +-----+--------+
- -- 14、查询学过编号“1”课程和编号“2”课程的同学的学号、姓名;
- select
- sid,
- sname
- from
- student
- where sid in (
- select
- student_id
- from
- score
- where course_id in (1,2)
- group by
- student_id
- );
- +-----+-----------+
- | sid | sname |
- +-----+-----------+
- | 1 | 乔丹 |
- | 2 | 艾弗森 |
- | 3 | 科比 |
- | 4 | curry |
- | 5 | james |
- | 6 | 李瑞 |
- | 7 | 白雪 |
- | 8 | 无敌 |
- | 9 | 天剑 |
- | 10 | egon |
- | 11 | alex |
- +-----+-----------+
- -- 15、查询没有带过高年级的老师id和姓名;
- select
- *
- from
- teacher
- where tid not in (
- select
- tid
- from
- teach2cls
- inner join
- class
- on teach2cls.cid=class.cid
- where class.grade_id in (5,6)
- );
- +-----+--------+
- | tid | tname |
- +-----+--------+
- | 2 | 李四 |
- | 3 | 王五 |
- +-----+--------+
- -- 16、查询学过“张三”老师所教的所有课的同学的学号、姓名;
- select
- sid,
- sname
- from
- student
- where class_id in (
- select
- cid # 张三教过的班级id
- from
- teach2cls
- inner join
- teacher
- on teach2cls.tid=teacher.tid
- where teacher.tname='张三'
- );
- +-----+-----------+
- | sid | sname |
- +-----+-----------+
- | 1 | 乔丹 |
- | 2 | 艾弗森 |
- | 3 | 科比 |
- | 4 | curry |
- | 7 | 白雪 |
- | 8 | 无敌 |
- | 10 | egon |
- | 11 | alex |
- +-----+-----------+
- -- 17、查询带过超过2个班级的老师的id和姓名;
- select
- *
- from
- teacher
- where tid in (
- select
- tid
- from
- teach2cls
- group by
- tid
- having
- count(cid) >= 2
- );
- +-----+--------+
- | tid | tname |
- +-----+--------+
- | 1 | 张三 |
- | 2 | 李四 |
- | 3 | 王五 |
- | 4 | 赵六 |
- | 5 | 马七 |
- +-----+--------+
- -- 18、查询课程编号“2”的成绩比课程编号“1”课程低的所有同学的学号、姓名;
- select
- sid,
- sname
- from
- student
- where sid in(
- select
- t1.student_id
- from
- (select
- student_id,
- score as score_1
- from
- score
- where
- course_id=1) as t1
- inner join
- (select
- student_id,
- score as score_2
- from
- score
- where
- course_id=2) as t2
- on t1.student_id=t2.student_id
- where
- t2.score_2 > t1.score_1
- );
- +-----+-----------+
- | sid | sname |
- +-----+-----------+
- | 2 | 艾弗森 |
- | 3 | 科比 |
- +-----+-----------+
- -- 19、查询所带班级数最多的老师id和姓名;
- select
- *
- from
- teacher
- where tid in (
- select
- tid # 考虑带最多班级的是多个老师,老师的tid
- from
- teach2cls
- group by
- tid
- having
- count(cid)=(
- select # 得到最多班级数量
- count(cid)
- from
- teach2cls
- group by
- tid
- order by
- count(cid) desc
- limit 1
- )
- );
- +-----+--------+
- | tid | tname |
- +-----+--------+
- | 3 | 王五 |
- +-----+--------+
- -- 20、查询有课程成绩小于60分的同学的学号、姓名;
- select
- sid,
- sname
- from
- student
- where
- sid in (
- select
- distinct student_id
- from
- score
- where
- score.score < 60
- );
- +-----+--------+
- | sid | sname |
- +-----+--------+
- | 1 | 乔丹 |
- | 3 | 科比 |
- | 4 | curry |
- | 5 | james |
- | 6 | 李瑞 |
- | 7 | 白雪 |
- | 8 | 无敌 |
- | 9 | 天剑 |
- | 10 | egon |
- +-----+--------+
- -- 21、查询没有学全所有课的同学的学号、姓名;
- select
- sid,
- sname
- from
- student
- where sid in (
- select
- student_id
- from
- score
- group by student_id
- having count(course_id) < (
- select
- count(cid)
- from
- course
- )
- );
- +-----+--------+
- | sid | sname |
- +-----+--------+
- | 4 | curry |
- | 5 | james |
- | 6 | 李瑞 |
- | 7 | 白雪 |
- | 8 | 无敌 |
- | 9 | 天剑 |
- | 10 | egon |
- | 11 | alex |
- +-----+--------+
- -- 22、查询至少有一门课与学号为“1”的同学所学相同的同学的学号和姓名;
- select
- sid,
- sname
- from
- student
- where sid in (
- select
- distinct student_id
- from
- score
- where course_id in (
- select
- course_id # 找出学号1锁学得所有课程
- from
- score
- where
- student_id=1
- ) and student_id!=1 # 排除掉学号为1的学生
- );
- +-----+-----------+
- | sid | sname |
- +-----+-----------+
- | 2 | 艾弗森 |
- | 3 | 科比 |
- | 4 | curry |
- | 5 | james |
- | 6 | 李瑞 |
- | 7 | 白雪 |
- | 8 | 无敌 |
- | 9 | 天剑 |
- | 10 | egon |
- | 11 | alex |
- +-----+-----------+
- -- 23、查询至少学过学号为“1”同学所选课程中任意一门课的其他同学学号和姓名;
- select
- sid,
- sname
- from
- student
- where sid in (
- select
- distinct student_id
- from
- score
- where course_id in (
- select
- course_id # 找出学号1锁学得所有课程
- from
- score
- where
- student_id=1
- ) and student_id!=1 # 排除掉学号为1的学生
- );
- +-----+-----------+
- | sid | sname |
- +-----+-----------+
- | 2 | 艾弗森 |
- | 3 | 科比 |
- | 4 | curry |
- | 5 | james |
- | 6 | 李瑞 |
- | 7 | 白雪 |
- | 8 | 无敌 |
- | 9 | 天剑 |
- | 10 | egon |
- | 11 | alex |
- +-----+-----------+
- -- 24、查询和“2”号同学学习的课程完全相同的其他同学的学号和姓名;
- select
- sid,
- sname
- from
- student
- where
- sid in (
- select
- score.student_id
- from
- score
- inner join
- (select
- course_id # 课程id
- from
- score
- where
- student_id = 2) as t1
- where
- score.course_id = t1.course_id
- and
- score.student_id != 2
- group by
- score.student_id
- having
- count(score.course_id) = (
- select # 学号2所学课程总数
- count(course_id)
- from
- score
- where
- student_id =2
- )
- );
- +-----+--------+
- | sid | sname |
- +-----+--------+
- | 1 | 乔丹 |
- | 3 | 科比 |
- +-----+--------+
- -- 25、删除学习“张三”老师课的score表记录;
- select
- course.cid
- from
- course
- left join
- teacher
- on course.teacher_id=teacher.tid
- where
- teacher.tname='张三';
- +-----+
- | cid |
- +-----+
- | 1 |
- | 2 |
- +-----+
- # 删除course_id为1,2的记录
- delete from
- score
- where
- course_id in (
- select
- course.cid
- from
- course
- left join
- teacher
- on course.teacher_id=teacher.tid
- where
- teacher.tname='张三'
- );
- +-----+------------+-----------+-------+
- | sid | student_id | course_id | score |
- +-----+------------+-----------+-------+
- | 3 | 1 | 3 | 58 |
- | 4 | 1 | 4 | 71 |
- | 5 | 1 | 5 | 68 |
- | 6 | 1 | 6 | 100 |
- | 9 | 2 | 3 | 71 |
- | 10 | 2 | 4 | 68 |
- | 11 | 2 | 5 | 92 |
- | 12 | 2 | 6 | 88 |
- | 15 | 3 | 3 | 72 |
- | 16 | 3 | 4 | 88 |
- | 17 | 3 | 5 | 92 |
- | 18 | 3 | 6 | 12 |
- | 20 | 4 | 4 | 78 |
- | 21 | 4 | 5 | 34 |
- | 23 | 5 | 4 | 38 |
- | 24 | 5 | 5 | 44 |
- | 26 | 6 | 4 | 32 |
- | 27 | 6 | 5 | 0 |
- | 29 | 7 | 3 | 60 |
- | 30 | 7 | 6 | 45 |
- | 32 | 8 | 3 | 65 |
- | 33 | 8 | 6 | 99 |
- | 35 | 9 | 3 | 69 |
- | 36 | 9 | 5 | 78 |
- | 38 | 10 | 3 | 69 |
- | 39 | 10 | 5 | 90 |
- | 41 | 11 | 3 | 89 |
- | 42 | 11 | 5 | 100 |
- +-----+------------+-----------+-------+
- -- 26、向score表中插入一些记录,这些记录要求符合以下条件:①没有上过编号“2”课程的同学学号;②插入“2”号课程的平均成绩;
- select
- sid
- from
- student
- where
- sid not in (
- select
- student_id
- from
- score
- where
- course_id =2
- );
- +-----+
- | sid |
- +-----+
- | 1 |
- | 2 |
- | 3 |
- | 4 |
- | 5 |
- | 6 |
- | 7 |
- | 8 |
- | 9 |
- | 10 |
- | 11 |
- +-----+
- select
- avg(score) as avg_score
- from
- score
- where
- course_id = 2;
- +-----------+
- | avg_score |
- +-----------+
- | NULL |
- +-----------+
- insert into score(student_id, course_id, score)
- select
- t1.sid,
- 2,
- t2.avg_score
- from
- (select
- sid
- from
- student
- where
- sid not in (
- select
- student_id
- from
- score
- where
- course_id =2
- )
- ) as t1,
- (select
- avg(score) as avg_score
- from
- score
- where
- course_id = 2
- ) as t2;
- # 增加以下记录
- +-----+------------+-----------+-------+
- | sid | student_id | course_id | score |
- +-----+------------+-----------+-------+
- | 3 | 1 | 3 | 58 |
- .......
- |
- | 42 | 11 | 5 | 100 |
- | 43 | 1 | 2 | NULL |
- | 44 | 2 | 2 | NULL |
- | 45 | 3 | 2 | NULL |
- | 46 | 4 | 2 | NULL |
- | 47 | 5 | 2 | NULL |
- | 48 | 6 | 2 | NULL |
- | 49 | 7 | 2 | NULL |
- | 50 | 8 | 2 | NULL |
- | 51 | 9 | 2 | NULL |
- | 52 | 10 | 2 | NULL |
- | 53 | 11 | 2 | NULL |
- +-----+------------+-----------+-------+
- # 将这些空值都修改为73
- -- 27、按平均成绩从低到高显示所有学生的“语文”、“数学”、“英语”三门的课程成绩,按如下形式显示: 学生ID,语文,数学,英语,有效课程数,有效平均分;
- # 这个题难度很大
- select
- main_score.student_id,
- (select
- score.score
- from
- score
- left join
- course
- on score.course_id=course.cid
- where
- course.cname='语文'
- and score.student_id=main_score.student_id) as chinese,
- (select
- score.score
- from
- score
- left join
- course
- on score.course_id=course.cid
- where
- course.cname='数学'
- and score.student_id=main_score.student_id) as math,
- (select
- score.score
- from
- score
- left join
- course
- on score.course_id=course.cid
- where
- course.cname='英语'
- and score.student_id=main_score.student_id) as english,
- count(main_score.course_id),
- avg(main_score.score)
- from
- score as main_score
- group by
- main_score.student_id
- order by # 注意order的拼写
- avg(main_score.score) ASC;
- +------------+---------+------+---------+-----------------------------+-----------------------+
- | student_id | chinese | math | english | count(main_score.course_id) | avg(main_score.score) |
- +------------+---------+------+---------+-----------------------------+-----------------------+
- | 6 | 32 | 0 | NULL | 3 | 35.0000 |
- | 5 | 38 | 44 | NULL | 3 | 51.6667 |
- | 7 | NULL | NULL | NULL | 3 | 59.3333 |
- | 4 | 78 | 34 | NULL | 3 | 61.6667 |
- | 3 | 88 | 92 | NULL | 5 | 67.4000 |
- | 9 | NULL | 78 | NULL | 3 | 73.3333 |
- | 1 | 71 | 68 | NULL | 5 | 74.0000 |
- | 10 | NULL | 90 | NULL | 3 | 77.3333 |
- | 2 | 68 | 92 | NULL | 5 | 78.4000 |
- | 8 | NULL | NULL | NULL | 3 | 79.0000 |
- | 11 | NULL | 100 | NULL | 3 | 87.3333 |
- +------------+---------+------+---------+-----------------------------+-----------------------+
- -- 28、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
- course_id,
- max(score.score) as max_score,
- min(score.score) as min_score
- from
- course
- left join
- score
- on course.cid=score.course_id
- group by
- score.course_id;
- +-----------+-----------+-----------+
- | course_id | max_score | min_score |
- +-----------+-----------+-----------+
- | NULL | NULL | NULL |
- | 2 | 73 | 73 |
- | 3 | 89 | 58 |
- | 4 | 88 | 32 |
- | 5 | 100 | 0 |
- | 6 | 100 | 12 |
- +-----------+-----------+-----------+
- -- 29、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
- course_id,
- avg(score) as avg_score
- from
- score
- group by
- course_id
- order by
- avg(score) desc;
- +-----------+-----------+
- | course_id | avg_score |
- +-----------+-----------+
- | 2 | 73.0000 |
- | 3 | 69.1250 |
- | 6 | 68.8000 |
- | 5 | 66.4444 |
- | 4 | 62.5000 |
- +-----------+-----------+
- -- 30、课程平均分从高到低显示(显示任课老师);
- select
- t2.cid,
- t2.cname,
- t2.avg_score,
- teacher.tname
- from
- teacher
- right join (
- select
- course.cid,
- course.cname,
- t1.avg_score,
- course.teacher_id
- from
- course
- inner join (
- select
- course_id,
- avg(score) avg_score
- from
- score
- group by
- course_id
- ) as t1
- on course.cid=t1.course_id
- ) as t2
- on teacher.tid=t2.teacher_id
- order by
- t2.avg_score desc;
- +-----+--------+-----------+--------+
- | cid | cname | avg_score | tname |
- +-----+--------+-----------+--------+
- | 2 | 体育 | 73.0000 | 张三 |
- | 3 | 物理 | 69.1250 | 李四 |
- | 6 | 外语 | 68.8000 | 马七 |
- | 5 | 数学 | 66.4444 | 赵六 |
- | 4 | 语文 | 62.5000 | 王五 |
- +-----+--------+-----------+--------+
- -- 31、查询各科成绩前三名的记录(不考虑成绩并列情况)
- select
- score.sid,score.course_id,score.score,T.first_num,T.second_num
- from
- score
- left join (
- select
- sid,
- (select
- score
- from
- score as s2
- where s2.course_id = s1.course_id
- order by score desc
- limit 0,1) as first_num,
- (select
- score
- from
- score as s2
- where s2.course_id = s1.course_id
- order by score desc
- limit 3,1) as second_num
- from
- score as s1
- ) as T
- on score.sid =T.sid
- where score.score <= T.first_num and score.score >= T.second_num;
- +-----+-----------+-------+-----------+------------+
- | sid | course_id | score | first_num | second_num |
- +-----+-----------+-------+-----------+------------+
- | 43 | 2 | 73 | 73 | 73 |
- | 44 | 2 | 73 | 73 | 73 |
- | 45 | 2 | 73 | 73 | 73 |
- | 46 | 2 | 73 | 73 | 73 |
- | 47 | 2 | 73 | 73 | 73 |
- | 48 | 2 | 73 | 73 | 73 |
- | 49 | 2 | 73 | 73 | 73 |
- | 50 | 2 | 73 | 73 | 73 |
- | 51 | 2 | 73 | 73 | 73 |
- | 52 | 2 | 73 | 73 | 73 |
- | 53 | 2 | 73 | 73 | 73 |
- | 9 | 3 | 71 | 89 | 69 |
- | 15 | 3 | 72 | 89 | 69 |
- | 35 | 3 | 69 | 89 | 69 |
- | 38 | 3 | 69 | 89 | 69 |
- | 41 | 3 | 89 | 89 | 69 |
- | 4 | 4 | 71 | 88 | 68 |
- | 10 | 4 | 68 | 88 | 68 |
- | 16 | 4 | 88 | 88 | 68 |
- | 20 | 4 | 78 | 88 | 68 |
- | 11 | 5 | 92 | 100 | 90 |
- | 17 | 5 | 92 | 100 | 90 |
- | 39 | 5 | 90 | 100 | 90 |
- | 42 | 5 | 100 | 100 | 90 |
- | 6 | 6 | 100 | 100 | 45 |
- | 12 | 6 | 88 | 100 | 45 |
- | 30 | 6 | 45 | 100 | 45 |
- | 33 | 6 | 99 | 100 | 45 |
- +-----+-----------+-------+-----------+------------+
- # 需要进一步改进
- select
- course_id,
- (select
- score
- from
- score as s2
- where s2.course_id = s1.course_id
- order by score desc
- limit 1) as first_num,
- (select
- score
- from
- score as s2
- where s2.course_id = s1.course_id
- order by score desc
- limit 1,1) as secend_num,
- (select
- score
- from
- score as s2
- where s2.course_id = s1.course_id
- order by score desc
- limit 2,1) as third_num
- from
- score as s1;
- +-----------+-----------+------------+-----------+
- | course_id | first_num | secend_num | third_num |
- +-----------+-----------+------------+-----------+
- | 2 | 73 | 73 | 73 |
- | 2 | 73 | 73 | 73 |
- | 2 | 73 | 73 | 73 |
- | 2 | 73 | 73 | 73 |
- | 2 | 73 | 73 | 73 |
- | 2 | 73 | 73 | 73 |
- | 2 | 73 | 73 | 73 |
- | 2 | 73 | 73 | 73 |
- | 2 | 73 | 73 | 73 |
- | 2 | 73 | 73 | 73 |
- | 2 | 73 | 73 | 73 |
- | 3 | 89 | 72 | 71 |
- | 3 | 89 | 72 | 71 |
- | 3 | 89 | 72 | 71 |
- | 3 | 89 | 72 | 71 |
- | 3 | 89 | 72 | 71 |
- | 3 | 89 | 72 | 71 |
- | 3 | 89 | 72 | 71 |
- | 3 | 89 | 72 | 71 |
- | 4 | 88 | 78 | 71 |
- | 4 | 88 | 78 | 71 |
- | 4 | 88 | 78 | 71 |
- | 4 | 88 | 78 | 71 |
- | 4 | 88 | 78 | 71 |
- | 4 | 88 | 78 | 71 |
- | 5 | 100 | 92 | 92 |
- | 5 | 100 | 92 | 92 |
- | 5 | 100 | 92 | 92 |
- | 5 | 100 | 92 | 92 |
- | 5 | 100 | 92 | 92 |
- | 5 | 100 | 92 | 92 |
- | 5 | 100 | 92 | 92 |
- | 5 | 100 | 92 | 92 |
- | 5 | 100 | 92 | 92 |
- | 6 | 100 | 99 | 88 |
- | 6 | 100 | 99 | 88 |
- | 6 | 100 | 99 | 88 |
- | 6 | 100 | 99 | 88 |
- | 6 | 100 | 99 | 88 |
- +-----------+-----------+------------+-----------+
- select
- course_id
- from
- (select
- course_id,
- (select
- score
- from
- score as s2
- where s2.course_id = s1.course_id
- order by score desc
- limit 1) as first_num,
- (select
- score
- from
- score as s2
- where s2.course_id = s1.course_id
- order by score desc
- limit 1,1) as secend_num,
- (select
- score
- from
- score as s2
- where s2.course_id = s1.course_id
- order by score desc
- limit 2,1) as third_num
- from
- score as s1
- ) as T
- group by course_id;
- -- 32、查询每门课程被选修的学生数;
- select
- course_id,
- count(student_id)
- from
- score
- group by
- course_id;
- +-----------+-------------------+
- | course_id | count(student_id) |
- +-----------+-------------------+
- | 2 | 11 |
- | 3 | 8 |
- | 4 | 6 |
- | 5 | 9 |
- | 6 | 5 |
- +-----------+-------------------+
- -- 33、查询选修了2门以上课程的全部学生的学号和姓名;
- select
- sid,
- sname
- from
- student
- where sid in (
- select
- student_id
- from
- score
- group by
- student_id
- having count(course_id) > 2
- );
- +-----+-----------+
- | sid | sname |
- +-----+-----------+
- | 1 | 乔丹 |
- | 2 | 艾弗森 |
- | 3 | 科比 |
- | 4 | curry |
- | 5 | james |
- | 6 | 李瑞 |
- | 7 | 白雪 |
- | 8 | 无敌 |
- | 9 | 天剑 |
- | 10 | egon |
- | 11 | alex |
- +-----+-----------+
- -- 34、查询男生、女生的人数,按倒序排列;
- select
- gender,
- count(sid)
- from
- student
- group by gender
- order by count(sid) desc;
- +--------+------------+
- | gender | count(sid) |
- +--------+------------+
- | 男 | 6 |
- | 女 | 5 |
- +--------+------------+
- -- 35、查询姓“张”的学生名单;
- select
- *
- from
- student
- where
- sname='张%';
- Empty set (0.00 sec)
- -- 36、查询同名同姓学生名单,并统计同名人数;
- select
- sname,
- count(sid)
- from
- student
- group by
- sname
- having
- count(sid) > 1;
- Empty set (0.00 sec)
- -- 37、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
- course_id,
- avg(score)
- from
- score
- group by
- course_id
- order by
- avg(score), # 两种排序规则需要用逗号分隔
- course_id DESC;
- +-----------+------------+
- | course_id | avg(score) |
- +-----------+------------+
- | 4 | 62.5000 |
- | 5 | 66.4444 |
- | 6 | 68.8000 |
- | 3 | 69.1250 |
- | 2 | 73.0000 |
- +-----------+------------+
- -- 38、查询课程名称为“数学”,且分数低于60的学生姓名和分数;
- select
- student.sname,
- score.score
- from
- score
- inner join
- student
- on score.student_id=student.sid
- where score.course_id in (
- select
- cid
- from
- course
- where
- cname='数学'
- );
- +-----------+-------+
- | sname | score |
- +-----------+-------+
- | 乔丹 | 68 |
- | 艾弗森 | 92 |
- | 科比 | 92 |
- | curry | 34 |
- | james | 44 |
- | 李瑞 | 0 |
- | 天剑 | 78 |
- | egon | 90 |
- | alex | 100 |
- +-----------+-------+
- -- 39、查询课程编号为“3”且课程成绩在80分以上的学生的学号和姓名;
- select
- sid,
- sname
- from
- student
- where sid in (
- select
- student_id
- from
- score
- where
- course_id=3
- and score>=80
- );
- +-----+-------+
- | sid | sname |
- +-----+-------+
- | 11 | alex |
- +-----+-------+
- -- 40、求选修了课程的学生人数
- select
- course_id,
- count(student_id)
- from
- score
- group by
- course_id;
- +-----------+-------------------+
- | course_id | count(student_id) |
- +-----------+-------------------+
- | 2 | 11 |
- | 3 | 8 |
- | 4 | 6 |
- | 5 | 9 |
- | 6 | 5 |
- +-----------+-------------------+
- -- 41、查询选修“王五”老师所授课程的学生中,成绩最高和最低的学生姓名及其成绩;
- select
- *
- from
- (select
- *
- from
- student
- inner join
- (select
- student_id,
- score
- from
- score
- where
- course_id in (
- select
- cid
- from
- teacher
- inner join
- course
- on teacher.tid=course.teacher_id
- where
- tname='王五'
- )
- ) as t1
- on student.sid=t1.student_id
- order by
- score
- limit 1
- ) as t2
- union
- select
- *
- from
- (select
- *
- from
- student
- inner join
- (select
- student_id,
- score
- from
- score
- where
- course_id in (
- select
- cid
- from
- teacher
- inner join
- course
- on teacher.tid=course.teacher_id
- where
- tname='王五'
- )
- ) as t1
- on student.sid=t1.student_id
- order by
- score DESC
- limit 1
- ) as t3;
- +-----+--------+--------+----------+------------+-------+
- | sid | sname | gender | class_id | student_id | score |
- +-----+--------+--------+----------+------------+-------+
- | 6 | 李瑞 | 女 | 4 | 6 | 32 |
- | 3 | 科比 | 男 | 2 | 3 | 88 |
- +-----+--------+--------+----------+------------+-------+
- -- 42、查询各个课程及相应的选修人数;
- select
- cid,
- cname,
- t1.stu_num
- from
- course
- right join
- (select
- course_id,
- count(student_id) as stu_num
- from
- score
- group by
- course_id) as t1
- on course.cid=t1.course_id;
- +------+--------+---------+
- | cid | cname | stu_num |
- +------+--------+---------+
- | 2 | 体育 | 11 |
- | 3 | 物理 | 8 |
- | 4 | 语文 | 6 |
- | 5 | 数学 | 9 |
- | 6 | 外语 | 5 |
- +------+--------+---------+
- -- 43、查询不同课程但成绩相同的学生的学号、课程号、学生成绩;
- select
- *
- from
- score
- where
- score in (
- select
- score # 找到不同课程但是有相同分数的成绩数值
- from
- score
- group by
- score
- having
- count(course_id)>1
- )
- order by score;
- +-----+------------+-----------+-------+
- | sid | student_id | course_id | score |
- +-----+------------+-----------+-------+
- | 5 | 1 | 5 | 68 |
- | 10 | 2 | 4 | 68 |
- | 35 | 9 | 3 | 69 |
- | 38 | 10 | 3 | 69 |
- | 4 | 1 | 4 | 71 |
- | 9 | 2 | 3 | 71 |
- | 43 | 1 | 2 | 73 |
- | 44 | 2 | 2 | 73 |
- | 45 | 3 | 2 | 73 |
- | 46 | 4 | 2 | 73 |
- | 47 | 5 | 2 | 73 |
- | 48 | 6 | 2 | 73 |
- | 49 | 7 | 2 | 73 |
- | 50 | 8 | 2 | 73 |
- | 51 | 9 | 2 | 73 |
- | 52 | 10 | 2 | 73 |
- | 53 | 11 | 2 | 73 |
- | 20 | 4 | 4 | 78 |
- | 36 | 9 | 5 | 78 |
- | 12 | 2 | 6 | 88 |
- | 16 | 3 | 4 | 88 |
- | 11 | 2 | 5 | 92 |
- | 17 | 3 | 5 | 92 |
- | 6 | 1 | 6 | 100 |
- | 42 | 11 | 5 | 100 |
- +-----+------------+-----------+-------+
- -- 44、查询每门课程成绩最好的前两名学生id和姓名;
- select
- student.sid,
- student.sname,
- t2.course_id,
- t2.score,
- t2.first_score,
- t2.second_score
- from
- student
- inner join ( # 这里会出现成绩相同的情况,录入了超过了两名的学生!!
- select
- score.student_id,
- score.course_id,
- score.score,
- t1.first_score,
- t1.second_score
- from
- score
- inner join (
- select
- s1.sid,
- (select s2.score from score as s2 where s1.course_id = s2.course_id order by s2.score desc limit 0,1) as first_score,
- (select s3.score from score as s3 where s1.course_id = s3.course_id order by s3.score desc limit 1,1) as second_score
- from
- score as s1
- ) as t1 on score.sid = t1.sid
- where
- score.score in ( # ??在这,会超过两个!!
- t1.first_score,
- t1.second_score
- )
- ) as t2 on student.sid = t2.student_id;
- +-----+-----------+-----------+-------+-------------+--------------+
- | sid | sname | course_id | score | first_score | second_score |
- +-----+-----------+-----------+-------+-------------+--------------+
- | 1 | 乔丹 | 2 | 73 | 73 | 73 |
- | 2 | 艾弗森 | 2 | 73 | 73 | 73 |
- | 3 | 科比 | 2 | 73 | 73 | 73 |
- | 4 | curry | 2 | 73 | 73 | 73 |
- | 5 | james | 2 | 73 | 73 | 73 |
- | 6 | 李瑞 | 2 | 73 | 73 | 73 |
- | 7 | 白雪 | 2 | 73 | 73 | 73 |
- | 8 | 无敌 | 2 | 73 | 73 | 73 |
- | 9 | 天剑 | 2 | 73 | 73 | 73 |
- | 10 | egon | 2 | 73 | 73 | 73 |
- | 11 | alex | 2 | 73 | 73 | 73 |
- | 3 | 科比 | 3 | 72 | 89 | 72 |
- | 11 | alex | 3 | 89 | 89 | 72 |
- | 3 | 科比 | 4 | 88 | 88 | 78 |
- | 4 | curry | 4 | 78 | 88 | 78 |
- | 2 | 艾弗森 | 5 | 92 | 100 | 92 |
- | 3 | 科比 | 5 | 92 | 100 | 92 |
- | 11 | alex | 5 | 100 | 100 | 92 |
- | 1 | 乔丹 | 6 | 100 | 100 | 99 |
- | 8 | 无敌 | 6 | 99 | 100 | 99 |
- +-----+-----------+-----------+-------+-------------+--------------+
- -- 45、检索至少选修两门课程的学生学号;
- select
- student_id
- from
- score
- group by
- student_id
- having
- count(course_id)>=2;
- +------------+
- | student_id |
- +------------+
- | 1 |
- | 2 |
- | 3 |
- | 4 |
- | 5 |
- | 6 |
- | 7 |
- | 8 |
- | 9 |
- | 10 |
- | 11 |
- +------------+
- -- 46、查询没有学生选修的课程的课程号和课程名;
- select
- cid,
- cname
- from
- course
- where
- cid not in (
- select
- course_id
- from
- score
- group by
- course_id
- );
- +-----+--------+
- | cid | cname |
- +-----+--------+
- | 1 | 生物 |
- +-----+--------+
- -- 47、查询没带过任何班级的老师id和姓名;
- select
- tid,
- tname
- from
- teacher
- where
- tid not in(
- select
- tid
- from
- teach2cls
- group by
- tid
- );
- Empty set (0.00 sec)
- -- 48、查询有两门以上课程超过80分的学生id及其平均成绩;
- select
- student_id,
- avg(score) as avg_score
- from
- score
- where score.student_id in
- (select
- student_id # 找到有两门课大于80的学号
- from
- (select
- *
- from
- score
- where
- score>80) as t1
- group by
- student_id
- having
- count(course_id) >= 2
- )
- group by student_id;
- +------------+-----------+
- | student_id | avg_score |
- +------------+-----------+
- | 2 | 78.4000 |
- | 3 | 67.4000 |
- | 11 | 87.3333 |
- +------------+-----------+
- -- 49、检索“3”课程分数小于60,按分数降序排列的同学学号;
- select
- student_id
- from
- score
- where
- course_id=3
- and score<60
- order by score DESC;
- +------------+
- | student_id |
- +------------+
- | 1 |
- +------------+
- -- 50、删除编号为“2”的同学的“1”课程的成绩;
- select
- sid
- from
- score
- where
- student_id=2
- and course_id=1;
- delete from
- score
- where
- sid in (
- select
- sid
- from
- score
- where
- student_id=2
- and course_id=1
- );
- ERROR 1093 (HY000): You can't specify target table 'score' for update in FROM clause'
- delete from
- score
- where
- sid in (
- select
- t1.sid
- from (
- select
- sid
- from
- score
- where
- student_id=2
- and course_id=1
- ) as t1
- );
- Query OK, 0 rows affected (0.00 sec)
- -- 51、查询同时选修了物理课和生物课的学生id和姓名;
- select
- cid
- from
- course
- where
- cname='物理'
- or cname='生物';
- +-----+--------+------------+
- | cid | cname | teacher_id |
- +-----+--------+------------+
- | 1 | 生物 | 1 |
- | 3 | 物理 | 2 |
- +-----+--------+------------+
- select
- sid,
- sname
- from
- student
- where
- sid in (
- select
- student_id
- FROM
- score
- where
- course_id in (
- select
- cid
- from
- course
- where
- cname='物理'
- or cname='生物'
- )
- group by
- student_id
- having
- count(course_id)=2
- );
- Empty set (0.00 sec)
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