多表查询练习
导出现有数据库数据：
- mysqldump -u用户名 -p密码 数据库名称 > 导出文件路径 # 结构+数据
- mysqldump -u用户名 -p密码 -d 数据库名称 > 导出文件路径 # 结构
导入现有数据库数据：
- mysql -uroot -p密码 数据库名称 < 文件路径
1.准备数据：init.sql文件内容：
/* 数据导入： Navicat Premium Data Transfer Source Server : localhost Source Server Type : MySQL Source Server Version : 50624 Source Host : localhost Source Database : sqlexam Target Server Type : MySQL Target Server Version : 50624 File Encoding : utf-8 Date: 10/21/2016 06:46:46 AM */ SET NAMES utf8; SET FOREIGN_KEY_CHECKS = 0; -- ---------------------------- -- Table structure for `class` -- ---------------------------- DROP TABLE IF EXISTS `class`; CREATE TABLE `class` ( `cid` int(11) NOT NULL AUTO_INCREMENT, `caption` varchar(32) NOT NULL, PRIMARY KEY (`cid`) ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of `class` -- ---------------------------- BEGIN; INSERT INTO `class` VALUES ('1', '三年二班'), ('2', '三年三班'), ('3', '一年二班'), ('4', '二年九班'); COMMIT; -- ---------------------------- -- Table structure for `course` -- ---------------------------- DROP TABLE IF EXISTS `course`; CREATE TABLE `course` ( `cid` int(11) NOT NULL AUTO_INCREMENT, `cname` varchar(32) NOT NULL, `teacher_id` int(11) NOT NULL, PRIMARY KEY (`cid`), KEY `fk_course_teacher` (`teacher_id`), CONSTRAINT `fk_course_teacher` FOREIGN KEY (`teacher_id`) REFERENCES `teacher` (`tid`) ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of `course` -- ---------------------------- BEGIN; INSERT INTO `course` VALUES ('1', '生物', '1'), ('2', '物理', '2'), ('3', '体育', '3'), ('4', '美术', '2'); COMMIT; -- ---------------------------- -- Table structure for `score` -- ---------------------------- DROP TABLE IF EXISTS `score`; CREATE TABLE `score` ( `sid` int(11) NOT NULL AUTO_INCREMENT, `student_id` int(11) NOT NULL, `course_id` int(11) NOT NULL, `num` int(11) NOT NULL, PRIMARY KEY (`sid`), KEY `fk_score_student` (`student_id`), KEY `fk_score_course` (`course_id`), CONSTRAINT `fk_score_course` FOREIGN KEY (`course_id`) REFERENCES `course` (`cid`), CONSTRAINT `fk_score_student` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`) ) ENGINE=InnoDB AUTO_INCREMENT=53 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of `score` -- ---------------------------- BEGIN; 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'); COMMIT; -- ---------------------------- -- Table structure for `student` -- ---------------------------- DROP TABLE IF EXISTS `student`; CREATE TABLE `student` ( `sid` int(11) NOT NULL AUTO_INCREMENT, `gender` char(1) NOT NULL, `class_id` int(11) NOT NULL, `sname` varchar(32) NOT NULL, PRIMARY KEY (`sid`), KEY `fk_class` (`class_id`), CONSTRAINT `fk_class` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`) ) ENGINE=InnoDB AUTO_INCREMENT=17 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of `student` -- ---------------------------- BEGIN; 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'); COMMIT; -- ---------------------------- -- Table structure for `teacher` -- ---------------------------- DROP TABLE IF EXISTS `teacher`; CREATE TABLE `teacher` ( `tid` int(11) NOT NULL AUTO_INCREMENT, `tname` varchar(32) NOT NULL, PRIMARY KEY (`tid`) ) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of `teacher` -- ---------------------------- BEGIN; 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'); COMMIT; SET FOREIGN_KEY_CHECKS = 1;准备数据 2.从init.sql文件中导入数据
- #准备表、记录
- mysql> create database db1;
- mysql> use db1;
- mysql> source /root/init.sql
3.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、查询物理课程比生物课程高的学生的学号 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、查询之选修了一门课程的学生姓名和学号 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前两名学生姓名 21、查询不同课程但成绩相同的学号，课程号，成绩 22、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； 23、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； 24、任课最多的老师中学生单科成绩最高的学生姓名4.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 inner join teacher on course.teacher_id = teacher.tid; #2、查询学生表中男女生各有多少人 select gender, count(1) # 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 from student where sid in( select t1.student_id from score t1 inner join( select cid from course where cname = '物理' ) t2 on t1.course_id = t2.cid where t1.num = 100 ); #4、查询平均成绩大于八十分的同学的姓名和平均成绩 select t1.sname, t2.avg_num from student as t1 inner join( select student_id, avg(num) as avg_num from score group by student_id having avg(num) > 80 ) as t2 on t1.sid = t2.student_id; #5、查询所有学生的学号，姓名，选课数，总成绩(注意：对于那些没有选修任何课程的学生也算在内) select t1.sid, t1.sname, t2.count_course, t2.sum_num from student as t1 left join( select student_id, count(course_id) as count_course, sum(num) as sum_num from score group by student_id ) as t2 on t1.sid = t2.student_id; #6、 查询姓李老师的个数 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 distinct student_id from score where course_id in ( select cid from course inner join teacher on course.teacher_id = teacher.tid where teacher.tname = '李平老师' ) ); #8、 查询物理课程比生物课程高的学生的学号(分别得到物理成绩表与生物成绩表，然后连表即可) select t1.student_id, t1.num, t2.num from ( select student_id, num from score where course_id = ( select cid from course where cname = '物理' ) ) as t1 inner join ( select student_id, num from score where course_id = ( select cid from course where cname = '生物' ) ) as t2 on t1.student_id = t2.student_id 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 # 包含了物理，体育都没选得 select sname from student where sid not in ( select t1.student_id from ( select student_id, course_id from score where course_id in ( select cid from course where cname in ( '物理', '体育' ) ) ) as t1 group by t1.student_id having count(t1.student_id) = 2 ); # 只选修了一门 select sname from student where sid in ( select t1.student_id from ( select student_id, course_id from score where course_id in ( select cid from course where cname in ( '物理', '体育' ) ) ) as t1 group by t1.student_id having count(t1.student_id) = 1 ); # 另一种方法： SELECT student.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 = '体育' ) GROUP BY student_id HAVING COUNT(course_id) = 1 ); #10、查询挂科超过两门(包括两门)的学生姓名和班级 select t1.caption, t2.sname from class as t1 inner join ( select sname, class_id from student where sid in ( select student_id from score where num < 60 group by student_id having count(sid) >= 2 ) ) as t2 on t1.cid = t2.class_id; #另一种方法： SELECT student.sname, class.caption FROM student INNER JOIN ( SELECT student_id FROM score WHERE num < 60 GROUP BY student_id HAVING count(course_id) >= 2 ) AS t1 INNER JOIN class ON student.sid = t1.student_id AND student.class_id = class.cid; #11、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(sid) = ( select count(cid) from course ) ); #12、查询李平老师教的课程的所有成绩记录 select * from score where course_id in ( select cid from course inner join teacher on course.teacher_id = teacher.tid where teacher.tname = '李平老师' ); #13、查询全部学生都选修了的课程号和课程名(取所有学生数，然后基于score表的课程分组，找出count(student_id)等于学生数即可) select cid, cname from course where cid in ( select course_id from score group by course_id having count(sid) = (select count(sid) from student) ); #14、查询每门课程被选修的次数 select course_id, count(sid) from score right join course on score.course_id = course.cid group by course_id order by course_id; SELECT course_id, COUNT(student_id) FROM score GROUP BY course_id; #15、查询之选修了一门课程的学生姓名和学号 select sid, sname from student where sid in ( select student_id from score group by student_id having count(sid) = 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 student.sname, t1.avg_num from student inner join ( select student_id, avg(num) as avg_num from score group by student_id having avg(num) > 85 ) as t1 on student.sid = t1.student_id; #18、查询生物成绩不及格的学生姓名和对应生物分数 select sname, t1.num from student inner join ( select student_id, num from score inner join course on score.course_id = course.cid where course.cname = '生物' and score.num < 60 ) as t1 on student.sid = t1.student_id; # 另一种方法： select student.sname, score.num from score left join course on score.course_id = course.cid left join student on score.student_id = student.sid where course.cname = '生物' and score.num < 60; #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, t1.avg_num from student inner join ( select student_id, avg(num) as avg_num from score where course_id in ( select cid from course inner join teacher on course.teacher_id = teacher.tid where teacher.tname = '李平老师' ) group by student_id order by avg_num desc limit 1 ) as t1 on student.sid = t1.student_id; #20、查询每门课程成绩最好的前两名学生姓名 select student.sname, num_table.course_id, num_table.first_num, num_table.second_num from student inner join ( select score.sid, score.course_id as course_id, score.student_id, t.first_num as first_num, t.second_num as second_num from score left join ( select sid, (select num from score as s2 where s2.course_id = s1.course_id order by num desc limit 0,1) as first_num, (select num from score as s3 where s3.course_id = s1.course_id order by num desc limit 1,1) as second_num from score as s1 ) as t on score.sid = t.sid where score.num <= t.first_num and score.num >= t.second_num ) as num_table on student.sid = num_table.student_id; #21、查询不同课程但成绩相同的学号，课程号，成绩 select distinct s1.student_id, s1.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; select distinct * from score as s1, score as s2 where 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 student.sname, course.cname from ( select student_id, course_id from score where course_id not in ( select cid from course inner join teacher on course.teacher_id = teacher.tid where teacher.tname = '李平老师' ) ) as t1 inner join course on t1.course_id = course.cid inner join student on t1.student_id = student.sid order by student.sname; #23、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 student_id, sname, count(course_id) from score left join student on score.student_id = student.sid where student_id != 1 and course_id in ( select course_id from score where student_id = 1 ) group by student_id # 另一种方法： 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 ) ) and sid !=1 #24、任课最多的老师中学生单科成绩最高的学生姓名 select sid, sname from student where sid in ( select distinct t1.id_students from ( select group_concat(student_id) as id_students, course_id, max(num) from score where course_id in ( select cid from course where teacher_id in ( select teacher_id from course group by teacher_id having count(cid) = ( select count(cid) from course group by teacher_id order by count(cid) desc limit 1 ) ) ) group by course_id ) as t1 );