一, 建表:
- /*
- 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;
导入的 sql 代码
拷贝上述代码, 新建一个. sql 文件, 保存到桌面
打开 navicat 新建数据库 day41, 选中新建的数据库鼠标右键选择运行 SQL 文件
弹出文件框, 选中刚刚保存到桌面的. sql 文件即可
二, 练习
1, 查询所有的课程的名称以及对应的任课老师姓名
4, 查询平均成绩大于八十分的同学的姓名和平均成绩
7, 查询没有报李平老师课的学生姓名
8, 查询没有同时选修物理课程和体育课程的学生姓名
9, 查询挂科超过两门 (包括两门) 的学生姓名和班级
- # 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
- INNER JOIN teacher ON course.teacher_id = teacher.tid;
- #4, 查询平均成绩大于八十分的同学的姓名和平均成绩
1. 根据 id 直接合并学生表和成绩表
2. 根据人头分组, 筛选平均成大于 80 的, 取出名字和平均成绩
- SELECT student.sname,AVG( num ) FROM
- student INNER JOIN score ON student_id = student.sid
- GROUP BY student.sid HAVING AVG( num )> 80;
1. 对成绩表以人头分组, 取平均成绩大于 80 的学生, 取出学生 id 和平均成绩
2. 将 1 中取出的数据和学生表进行内连接, 两个 id 对上, 从中取出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 )> 80 ) AS t1
- ON student.sid = t1.student_id;
- #7, 查询没有报李平老师课的学生姓名(找出报名李平老师课程的学生, 然后取反就可以)
1. 老师为李平的前提下, 合并课程和老师表, 取出课程 id(全是利平的课)作为表 t1
2. 内连接 t1 和成绩表, 得到的全是报李平课的学生, 取出学生 id,
3. 学生表中根据筛选出的学生 id, 取反, 取出学生名字
- select student.sname from student where student.sid not in
- (select score.student_id from score inner join
- (select course.cid as t1_cid,course.cname from course inner join teacher on course.teacher_id=teacher.tid where teacher.tname='李平老师') as t1
- on score.course_id=t1.t1_cid)
- ;
1. 老师为李平的前提下, 合并课程和老师表, 取出课程 id(全是利平的课)
2. 从成绩表中取出课程 id 在 t1 表中的学生的 id
3. 从学生表中取出学生 id 不在其中的学生名字
- SELECT student.sname FROM student WHERE sid NOT IN (
- SELECT DISTINCT student_id FROM score
- WHERE course_id IN ( SELECT course.cid FROM course INNER JOIN teacher ON course.teacher_id = teacher.tid WHERE teacher.tname = '李平老师' )
- );
- #8, 查询没有同时选修物理课程和体育课程的学生姓名(没有同时选修指的是选修了一门的, 思路是得到物理 + 体育课程的学生信息表, 然后基于学生分组, 统计 count(课程)=1)
1. 课程表中得到物理和体育的课程号
2. 从成绩表中选出课程号对的上且每个人的 id 计数为 1(即只报一门课)的学生 id
3. 根据陈学生 id 从学生表中得到名字
- select student.sname from student where student.sid in
- (select score.student_id from score where score.course_id in
- (select course.cid from course where
- course.cname='物理' or course.cname='体育')
- group by score.student_id having count(score.student_id)=1 )
- ;
- # 9, 查询挂科超过两门 (包括两门) 的学生姓名和班级
- select student.sname,class.caption from class INNER JOIN student
- on class.cid = student.class_id
- WHERE student.sid in
- (select student_id from score where num <60
- GROUP BY student_id
- HAVING COUNT(course_id)>=2)
- ;
- select class.caption,t1.sname from class inner join
- (select student.sname,student.class_id from student where student.sid in
- (select score.student_id from score where num <60
- group by score.student_id having count(score.student_id)>1 )) as t1
- on class.cid=t1.class_id
- ;
来源: http://www.bubuko.com/infodetail-3166238.html