连表操作
例子：综合练习
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;
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
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 、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 题目
1、查询所有的课程的名称以及对应的任课老师姓名 select cname,tname from course left 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(sid) from student group by gender; 3、查询物理成绩等于100的学生的姓名 #子查询的方式 select sname from student where sid in ( select student_id from score where course_id = (select cid from course where cname='物理') and num=100 ); #连表的方式 select sname from student inner join ( select student_id from score where course_id = (select cid from course where cname='物理') and num=100 ) as a on a.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 student.sname,t1.平均成绩 from student inner join (select student_id,avg(num) 平均成绩 from score group by student_id having avg(num) > 80) as t1 on student.sid=t1.student_id; 5、查询所有学生的学号，姓名，选课数，总成绩 select student.sid,sname 学生名,选课数,总成绩 from student left join (select student_id,count(course_id) 选课数,sum(num) 总成绩 from score group by student_id) as t1 on student.sid=t1.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 where teacher_id=(select tid from teacher where tname='李平老师') ) ); 8、 查询物理课程比生物课程高的学生的学号 select t1.student_id from (select student_id,num from score inner join course on score.course_id=course.cid where course.cname='物理') as t1 inner join (select student_id,num from score inner join course on score.course_id=course.cid where course.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 select sname from student where sid in ( select student_id from score inner join course on course.cname in ('物理','体育') and course.cid=score.course_id group by student_id having count(course_id) !=2 ); 10、查询挂科超过两门(包括两门)的学生姓名和班级名字 select t2.sname,class.caption from (select sname,class_id from student inner join ( select student_id from score where num < 60 group by student_id having count(course_id) >=2 ) as t1 on student.sid=t1.student_id) as t2 inner join class on class.cid = t2.class_id ; 11 、查询选修了所有课程的学生姓名 select sname from student inner join ( select student_id from score group by student_id having count(course_id) = (select count(cid) from course) ) t1 on t1.student_id = student.sid ; 12、查询李平老师教的课程的所有成绩记录 select student_id,course_id,num from score inner join ( select cid from course inner join teacher on teacher.tname='李平老师' and teacher.tid=course.teacher_id ) as t1 on t1.cid=score.course_id ; 13、查询全部学生都选修了的课程号和课程名 select course.cid,course.cname from course inner join ( select course_id from score group by course_id having count(student_id) = (select count(sid) from student) ) t1 on t1.course_id=course.cid ; 14、查询每门课程被选修的次数 select course.cname,选修人数 from course inner join ( select course_id,count(student_id) as 选修人数 from score group by course_id ) as t1 on t1.course_id=course.cid ; 15、查询之选修了一门课程的学生姓名和学号 select sid,sname from student inner join ( select student_id from score group by student_id having count(course_id)=1 ) t1 on t1.student_id = student.sid ; 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,avg_num from student inner join ( select student_id,avg(num) as avg_num from score group by student_id having avg(num) > 85 ) 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 student.sname,t1.num from student inner join ( select student_id,num from score where course_id=(select cid from course where cname='生物') and num < 60 ) t1 on t1.student_id=student.sid ; 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 student where sid = ( select student_id from score where course_id in ( select cid from course inner join teacher on teacher.tname='李平老师' and course.teacher_id=teacher.tid ) group by student_id order by avg(num) desc limit 1 );
！！！重中之重：练习之前务必搞清楚sql逻辑查询语句的执行顺序