Mysql--练习
学生选课系统
设计表关系
创建表和插入数据
/* Navicat MySQL Data Transfer Source Server : localhost_3306 Source Server Version : 50719 Source Host : localhost:3306 Source Database : oldbo Target Server Type : MYSQL Target Server Version : 50719 File Encoding : 65001 Date: 2017-07-26 15:46:16 */ 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 -- ---------------------------- INSERT INTO `class` VALUES ('1', '三年二班'); INSERT INTO `class` VALUES ('2', '三年三班'); INSERT INTO `class` VALUES ('3', '一年二班'); INSERT INTO `class` VALUES ('4', '二年九班'); -- ---------------------------- -- 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 -- ---------------------------- INSERT INTO `course` VALUES ('1', '生物', '1'); INSERT INTO `course` VALUES ('2', '物理', '2'); INSERT INTO `course` VALUES ('3', '体育', '3'); INSERT INTO `course` VALUES ('4', '美术', '2'); -- ---------------------------- -- 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 -- ---------------------------- INSERT INTO `score` VALUES ('1', '1', '1', '10'); INSERT INTO `score` VALUES ('2', '1', '2', '9'); INSERT INTO `score` VALUES ('5', '1', '4', '66'); INSERT INTO `score` VALUES ('6', '2', '1', '8'); INSERT INTO `score` VALUES ('8', '2', '3', '68'); INSERT INTO `score` VALUES ('9', '2', '4', '99'); INSERT INTO `score` VALUES ('10', '3', '1', '77'); INSERT INTO `score` VALUES ('11', '3', '2', '66'); INSERT INTO `score` VALUES ('12', '3', '3', '87'); INSERT INTO `score` VALUES ('13', '3', '4', '99'); INSERT INTO `score` VALUES ('14', '4', '1', '79'); INSERT INTO `score` VALUES ('15', '4', '2', '11'); INSERT INTO `score` VALUES ('16', '4', '3', '67'); INSERT INTO `score` VALUES ('17', '4', '4', '100'); INSERT INTO `score` VALUES ('18', '5', '1', '79'); INSERT INTO `score` VALUES ('19', '5', '2', '11'); INSERT INTO `score` VALUES ('20', '5', '3', '67'); INSERT INTO `score` VALUES ('21', '5', '4', '100'); INSERT INTO `score` VALUES ('22', '6', '1', '9'); INSERT INTO `score` VALUES ('23', '6', '2', '100'); INSERT INTO `score` VALUES ('24', '6', '3', '67'); INSERT INTO `score` VALUES ('25', '6', '4', '100'); INSERT INTO `score` VALUES ('26', '7', '1', '9'); INSERT INTO `score` VALUES ('27', '7', '2', '100'); INSERT INTO `score` VALUES ('28', '7', '3', '67'); INSERT INTO `score` VALUES ('29', '7', '4', '88'); INSERT INTO `score` VALUES ('30', '8', '1', '9'); INSERT INTO `score` VALUES ('31', '8', '2', '100'); INSERT INTO `score` VALUES ('32', '8', '3', '67'); INSERT INTO `score` VALUES ('33', '8', '4', '88'); INSERT INTO `score` VALUES ('34', '9', '1', '91'); INSERT INTO `score` VALUES ('35', '9', '2', '88'); INSERT INTO `score` VALUES ('36', '9', '3', '67'); INSERT INTO `score` VALUES ('37', '9', '4', '22'); INSERT INTO `score` VALUES ('38', '10', '1', '90'); INSERT INTO `score` VALUES ('39', '10', '2', '77'); INSERT INTO `score` VALUES ('40', '10', '3', '43'); INSERT INTO `score` VALUES ('41', '10', '4', '87'); INSERT INTO `score` VALUES ('42', '11', '1', '90'); INSERT INTO `score` VALUES ('43', '11', '2', '77'); INSERT INTO `score` VALUES ('44', '11', '3', '43'); INSERT INTO `score` VALUES ('45', '11', '4', '87'); INSERT INTO `score` VALUES ('46', '12', '1', '90'); INSERT INTO `score` VALUES ('47', '12', '2', '77'); INSERT INTO `score` VALUES ('48', '12', '3', '43'); INSERT INTO `score` VALUES ('49', '12', '4', '87'); INSERT INTO `score` VALUES ('52', '13', '3', '87'); -- ---------------------------- -- 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 -- ---------------------------- INSERT INTO `student` VALUES ('1', '男', '1', '理解'); INSERT INTO `student` VALUES ('2', '女', '1', '钢蛋'); INSERT INTO `student` VALUES ('3', '男', '1', '张三'); INSERT INTO `student` VALUES ('4', '男', '1', '张一'); INSERT INTO `student` VALUES ('5', '女', '1', '张二'); INSERT INTO `student` VALUES ('6', '男', '1', '张四'); INSERT INTO `student` VALUES ('7', '女', '2', '铁锤'); INSERT INTO `student` VALUES ('8', '男', '2', '李三'); INSERT INTO `student` VALUES ('9', '男', '2', '李一'); INSERT INTO `student` VALUES ('10', '女', '2', '李二'); INSERT INTO `student` VALUES ('11', '男', '2', '李四'); INSERT INTO `student` VALUES ('12', '女', '3', '如花'); INSERT INTO `student` VALUES ('13', '男', '3', '刘三'); INSERT INTO `student` VALUES ('14', '男', '3', '刘一'); INSERT INTO `student` VALUES ('15', '女', '3', '刘二'); INSERT INTO `student` VALUES ('16', '男', '3', '刘四'); -- ---------------------------- -- 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 -- ---------------------------- INSERT INTO `teacher` VALUES ('1', '张磊老师'); INSERT INTO `teacher` VALUES ('2', '李平老师'); INSERT INTO `teacher` VALUES ('3', '刘海燕老师'); INSERT INTO `teacher` VALUES ('4', '朱云海老师'); INSERT INTO `teacher` VALUES ('5', '李杰老师'); SET FOREIGN_KEY_CHECKS=1;
查询条件
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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 |
参考答案
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1、SELECT cname,tname FROM course LEFT JOIN teacher on course.teacher_id=teacher.tid2、SELECT gender 性别 ,COUNT(gender) 人数 from student GROUP BY gender;3、SELECT sname from student where sid in (SELECT student_id from score LEFT JOIN course ON score.course_id=course.cid WHERE num=100 AND course.cname="物理");4、SELECT sname 姓名,平均成绩 from student RIGHT JOIN (SELECT student_id,avg(num) 平均成绩 from score GROUP BY student_id HAVING avg(num)>80) as A on student.sid=A.student_id;5、SELECT student_id 学号,sname 姓名,COUNT(course_id) 课程数,SUM(num) 总分 FROM score LEFT JOIN student ON score.student_id=student.sid GROUP BY student_id;7、SELECT * FROM student WHERE sid not in (SELECT student_id FROM score WHERE course_id in (SELECT cid FROM course LEFT JOIN teacher ON teacher.tid=course.teacher_id WHERE tname like "李平%"))8、SELECT * FROM (SELECT * FROM score LEFT JOIN course ON score.course_id=course.cid WHERE cname="生物") as A INNER JOIN (SELECT * FROM score LEFT JOIN course ON score.course_id=course.cid WHERE cname="物理") as B ON A.student_id=B.student_id WHERE a.num<b.num9、SELECT sname from student WHERE sid NOT IN (SELECT student_id FROM score LEFT JOIN course ON score.course_id=course.cid WHERE cname='体育' OR cname='物理' GROUP BY student_id HAVING COUNT(course_id)>1) ;10、SELECT sname,gender from student WHERE sid in (SELECT student_id from score WHERE num<60 GROUP BY student_id HAVING COUNT(student_id)>1);11、SELECT sid 学号,sname 姓名 from student WHERE sid in (SELECT student_id FROM score GROUP BY student_id HAVING COUNT(student_id)!= (SELECT COUNT(cid) FROM course))12、SELECT * FROM score WHERE course_id NOT IN (SELECT cid from teacher INNER JOIN course on teacher.tid=course.teacher_id WHERE teacher.tname LIKE "李平%");13、SELECT course_id from score GROUP BY course_id HAVING COUNT(course_id)=(SELECT COUNT(sid) FROM student)14、-- SELECT course_id,COUNT(course_id) from score GROUP BY course_id SELECT cname,COUNT(course_id) FROM score LEFT JOIN course ON score.course_id=course.cid GROUP BY course_id15、SELECT sid,sname FROM student WHERE sid in (SELECT student_id from score GROUP BY student_id HAVING COUNT(sid)=1);16、SELECT DISTINCT num FROM score ORDER BY num DESC；17、SELECT sname from student WHERE sid in (SELECT student_id FROM score GROUP BY student_id HAVING AVG(num)>85) 注意：用这种方式我们无法查看对应的平均成绩，所以不得不使用连表： SELECT sname,AVG(num) FROM student LEFT JOIN score ON student.sid=score.student_id GROUP BY student_id HAVING AVG(num)>85;18、SELECT sname 姓名,num 生物成绩 FROM score LEFT JOIN course ON score.course_id=course.cid LEFT JOIN student ON score.student_id=student.sid WHERE score.num<60 AND cname="生物"；19、 SELECT student_id,avg(num),sname FROM score LEFT JOIN student ON score.student_id=student.sid WHERE course_id in (SELECT cid FROM course LEFT JOIN teacher ON teacher.tid=course.teacher_id WHERE tname LIKE "李平%") GROUP BY student_id ORDER BY AVG(num) DESC LIMIT 1 |
