MySql-多表查询练习
数据准备
/*
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;
表结构如下:
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 teacher_id = tid;
2、查询学生表中男女生各有多少人
select gender,count(*) num from student group by gender;
3、查询物理成绩等于100的学生的姓名
select sname from score join course join student on course_id = cid and student_id = student.sid where cname = '物理' and 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 sname,avg_num from student join
(select student_id, avg(num) avg_num from score group by student_id having avg(num) > 80) as t2
on sid = t2.student_id;
5、查询所有学生的学号，姓名，选课数，总成绩
select student.sid,sname,course_num,total_mark from student join
(select student_id,count(*) course_num,sum(num) total_mark from score group by student_id) as t
on sid = student_id;
6、 查询姓李老师的个数
select count(*) num 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 join teacher on tid = teacher_id 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 w.student_id from
（select student_id,num from score where course_id =
(select cid from course where cname = '物理')）as w
join
（select student_id,num from score where course_id =
(select cid from course where cname = '生物')) as s
on w.student_id = s.student_id where w.num > s.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 w.student_id from
(select student_id from score where course_id =
(select cid from course where cname = '物理')) as w
join
(select student_id from score where course_id =
(select cid from course where cname = '体育')) as s
on w.student_id = s.student_id);
10、查询挂科超过两门(包括两门)的学生姓名和班级
select sname,caption from student join
(select student_id from score where num < 60 group by student_id having count(*) >=2) as s
join class on class_id = cid and student_id = sid;
11、查询选修了所有课程的学生姓名
select sname from score join student on student_id = student.sid group by student_id having count(student_id) =
(select count(cid) course_num 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 teacher join course
on tid = teacher_id where tname = '李平老师');
13、查询全部学生都选修了的课程号和课程名
select course_id,cname from score join course on course_id = cid group by course_id having count(*) =
(select count(sid) from student);
14、查询每门课程被选修的次数
select cname,count(course_id) from score join course on cid = course_id group by course_id;
15、查询之选修了一门课程的学生姓名和学号
select student_id,sname from score join student on student.sid = student_id group by student_id having count(student_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,t.avg_num from student join
(select student_id, avg(num) avg_num from score group by student_id having avg(num) > 85) as t
on student.sid = t.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,t.num from student join
(select student_id,num from score join course on course_id = cid where num < 60 and cname = '生物') as t
on student.sid = t.student_id;
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 join
(select student_id,avg(num) from score where course_id in
(select cid from teacher join course on tid = teacher_id where tname = '李平老师')
group by student_id order by avg(num) desc limit 1) as t
on student.sid = student_id;
20、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 sid,sname from student where sid in
(select distinct student_id from score where course_id in
(select course_id from student join score on student.sid = student_id where student.sid = 1) and student_id != 1);
21、任课最多的老师中学生单科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 join
(select teacher_id,count(*) t_count from course group by teacher_id order by t_count desc limit 1) as t
on course.teacher_id = t.teacher_id) order by num desc limit 1;
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