MySql 查询强化练习

向右看齐 2021-11-09 09:01 345阅读 0赞

*  参考图

![表结构参考图][1692539-20190724232453235-1348871427.png]

## 1. 创建表 ##

-- 1. 创建班级表 create table class( cid int primary key auto_increment, caption varchar(32) not null )ENGINE=InnoDB DEFAULT CHARSET=utf8; -- 2. 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 )ENGINE=InnoDB DEFAULT CHARSET=utf8; -- 3. 创建老师表 create table teacher( tid int primary key auto_increment, tname varchar(32) not null )ENGINE=InnoDB DEFAULT CHARSET=utf8; -- 4. 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 )ENGINE=InnoDB DEFAULT CHARSET=utf8; -- 5. 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 )ENGINE=InnoDB DEFAULT CHARSET=utf8;

## 2. 各个表的数据准备 ##

-- 1. 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'); -- 2. 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'); -- 3. 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'); -- 4. 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'); -- 5. 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. 查询题目 ##

1、查询所有的课程的名称以及对应的任课老师姓名
    
    2、查询学生表中男女生各有多少人
    
    3、查询物理成绩等于100的学生的姓名
    
    4、查询平均成绩大于八十分的同学的姓名和平均成绩
    
    5、查询所有学生的学号，姓名，选课数，总成绩
    
    6、 查询姓李老师的个数
    
    7、 查询没有报李平老师课的学生姓名
    
    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
    
    9、 查询没有同时选修物理课程和体育课程的学生姓名
    
    10、查询挂科超过两门(包括两门)的学生姓名和班级
    
    11、查询选修了所有课程的学生姓名
    
    12、查询李平老师教的课程的所有成绩记录
    
    13、查询全部学生都选修了的课程号和课程名
    
    14、查询每门课程被选修的次数
    
    15、查询只选修了一门课程的学生学号和姓名
    
    16、查询所有学生考出的成绩并按从高到低排序（成绩去重）
    
    17、查询平均成绩大于85的学生姓名和平均成绩
    
    18、查询生物成绩不及格的学生姓名和对应生物分数
    
    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

## 4. 参考答案 ##

1、查询所有的课程的名称以及对应的任课老师姓名 select course.cname, teacher.tname from course, teacher where course.teacher_id = teacher.tid; 2、查询学生表中男女生各有多少人 select gender, count(sid) from student group by gender; 3、查询物理成绩等于100的学生的姓名 select sname, num from score, student where course_id = (select cid from course where cname = '物理') and num = 100 and score.student_id=student.sid; 4、查询平均成绩大于八十分的同学的姓名和平均成绩 select sname, avg(num) 平均成绩 from score, student where 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(course_id) 选课数, sum(num) 总成绩 from score, student where student_id=student.sid group by student_id; 6、 查询姓李老师的个数 select sum(case when tname like '李%' then 1 else 0 end) 李 from teacher; -- select count(tid) from teacher where tname like '李%'; 7、 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 = (select tid from teacher where tname='李平')) group by student_id); 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 select wl.student_id from (select student_id, num from score where course_id = (select cid from course where cname='物理')) as wl inner join (select student_id, num from score where course_id = (select cid from course where cname='生物')) as sw on wl.student_id = sw.student_id where wl.num > sw.num; 9、 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='物理' or cname='体育') group by student_id having count(sid)=2); 10、查询挂科超过两门(包括两门)的学生姓名和班级 select class_id, caption, sname from student, class where cid= class_id and sid in (select student_id from score where num < 60 group by student_id having count(student_id)>=2); 11、查询选修了所有课程的学生姓名 select sname from student where sid not in (select student_id from score group by student_id having count(course_id) = (select count(cid) from course)); 12、查询李平老师教的课程的所有成绩记录 select sname, cname, num from score, course, student where student_id=student.sid and course_id=course.cid and course_id in (select cid from course where teacher_id = (select tid from teacher where tname='李平')); 13、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(student_id)=(select count(sid) from student)); 14、查询每门课程被选修的次数 select count(student_id) 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 select sid, sname from student where sid in (select student_id from score group by student_id having count(course_id)=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） select distinct 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 select sname, avg(num) from score, student where 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 select sname, num from score, student where num < 60 and student_id=student.sid and course_id = (select cid from course where cname='生物'); 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 select sname from score, student where student_id=student.sid and course_id in (select cid from course where teacher_id = (select tid from teacher where tname='李平')) group by student_id order by sum(num) desc limit 1; 20、查询每门课程成绩最好的课程id、学生姓名和分数 select score.course_id, sname, num from student, score, (select course_id, max(num) as mnum from score group by course_id) as mnum_course where student_id=student.sid and mnum_course.course_id = score.course_id and mnum_course.mnum=score.num; 21、查询不同课程但成绩相同的课程号、学生号、成绩 select course_id, student_id, num from score as s1 where exists (select s2.course_id, s2.student_id, s2.num from score as s2 where s1.student_id = s2.student_id and s1.course_id != s2.course_id and s1.num = s2.num); 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 select sname, cname from score, course inner join student on where student.sid=score.student_id and course.cid=score.course_id and student.sid not in (select student_id from score where course_id in (select cid from course where teacher_id = (select tid from teacher where tname='李平')) group by student_id); 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 select student.sid, sname from student, score where student.sid=score.student_id and course_id in (select course_id from score where student_id=2) group by student_id; 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 select score.course_id, sname, num from student, score, -- 单科最高分 max_score (select course_id, max(num) as maxnum from score, -- 任课最多的老师 max_course_teacher (select teacher_id from course group by teacher_id order by count(teacher_id) desc limit 1) as max_course_teacher where course_id in (select cid from course where teacher_id = max_course_teacher.teacher_id) group by course_id) as max_score where student.sid=student_id and max_score.course_id = score.course_id and num = maxnum;

转载于:https://www.cnblogs.com/trent-fzq/p/11241565.html

[1692539-20190724232453235-1348871427.png]: /images/20211109/fc76466925ee4dcbb0777ea985201fd9.png