MySql之数据操作

导出现有的数据库数据：

　　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

导入现有的数据库数据：

　　mysqldum -uroot -p密码 数据库名称 < 文件路径

表结构和数据

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;


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');





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;


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');




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;


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');




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;


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');








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;


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');

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;


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');


SET FOREIGN_KEY_CHECKS = 1;




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;


INSERT INTO `class` VALUES ('1', '三年二班'), ('2', '三年三班'), ('3', '一年二班'), ('4', '二年九班');


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;


INSERT INTO `course` VALUES ('1', '生物', '1'), ('2', '物理', '2'), ('3', '体育', '3'), ('4', '美术', '2');
COMMIT;


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;


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');


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;


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;

2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；

select A.student_id,A.cname,A.num,B.cname,B.num 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.num

3、查询平均成绩大于60分的同学的学号，姓名和平均成绩；

SELECT B.student_id,student.sname,B.cc FROM
(SELECT student_id,avg(num) AS cc FROM score GROUP BY student_id HAVING avg(num) > 60) AS B
LEFT JOIN student ON B.student_id=student.sid

4、查询所有同学的学号、姓名、选课数、总成绩；

SELECT score.student_id,student.sname,count(score.student_id) AS 选课数,sum(num) AS 总成绩
FROM score
LEFT JOIN student ON score.student_id=student.sid
GROUP BY student_id

5、查询姓“李”的老师的个数；

SELECT count(1) FROM teacher WHERE tname LIKE '李%'

6、查询没学过“李平”老师课的同学的学号、姓名；

思路：

a.查到‘李平老师’的任教课程

SELECT cid,cname FROM course LEFT JOIN teacher ON course.teacher_id=teacher.tid WHERE tname='李平老师'

b.通过score表中，查到学习 ‘李平’老师课的同学ID

SELECT student_id FROM score 
WHERE course_id in 
(SELECT cid FROM course LEFT JOIN teacher ON course.teacher_id=teacher.tid WHERE tname='李平老师');

c.最后结果

SELECT sid,sname FROM student WHERE sid NOT IN 
( SELECT student_id FROM score WHERE course_id in 
	(SELECT cid FROM course LEFT JOIN teacher ON course.teacher_id=teacher.tid WHERE tname='李平老师')
)

select sid,sname from student where sid not in (
        select DISTINCT student_id from score where score.course_id in (
            select cid from course left join teacher on course.teacher_id = teacher.tid where tname = '李平老师'
        ) 
  )

7.查询学过“001”并且也学过编号“002”课程的同学的学号、姓名；

    思路：

            先查到既选择 1 又选择 2 课程的所有同学

            根据学生进行分组，如果学生数量等于2，表示两门都已选

SELECT student_id,sname FROM score
LEFT JOIN student ON score.student_id=student.sid
WHERE course_id IN (1,2) 
GROUP BY student_id HAVING count(student_id)>1

8、查询学过“李平”老师所教的所有课的同学的学号、姓名；

　　可将 6.，改为 in;

还可：

SELECT student_id,sname FROM score
LEFT JOIN student ON score.student_id=student.sid
WHERE course_id IN (SELECT cid FROM course LEFT JOIN teacher ON course.teacher_id=teacher.tid WHERE tname='李平老师')
GROUP BY student_id 
HAVING count(student_id)=(SELECT count(1) FROM course LEFT JOIN teacher ON course.teacher_id=teacher.tid 
WHERE tname='李平老师')

10、查询有课程成绩小于60分的同学的学号、姓名；

SELECT student.sid,sname FROM score 
LEFT JOIN student ON score.student_id=student.sid
WHERE num<60 
GROUP BY student.sid

11、查询没有学全所有课的同学的学号、姓名；

    思路：

        在分数表中根据学生进行分组，获取每一个学生选课数量

        如果数量 == 总课程数量，表示已经选择了所有课程

 

SELECT student_id,sname FROM score 
LEFT JOIN student ON score.student_id=student.sid
GROUP BY student_id
HAVING count(course_id)=(SELECT count(1) FROM course)

12.查询至少一门课与学号为‘001’的同学所学相同的同学的学号和姓名

　　思路：

　　　　获取 001 同学选择的所有课程

　　　　获取课程在其中的所有人以及所有课程

　　　　根据学生筛选，获取姓名

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
 

17.按平均成绩从低到高，显示所有学生的“语文”，“数学”，“英语”三门的课程成绩，按如下形式显示：学生ID，语文，数学，英语，课程数，平均分

18、查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分；

SELECT course_id,max(num) as 最高分,min(num) as 最低分 FROM score 
LEFT JOIN course ON score.course_id=course.cid
GROUP BY course_id

20、课程平均分从高到低显示（显示任课老师）；

SELECT course_id,avg(num),tname FROM score
LEFT JOIN course ON score.course_id=course.cid
LEFT JOIN teacher ON course.teacher_id=teacher.tid
GROUP BY course_id ORDER BY avg(num) DESC

22、查询每门课程被选修的学生数

SELECT course_id,cname,count(1) FROM score
LEFT JOIN course ON course.cid =score.course_id
GROUP BY  course_id

23、查询出只选修了一门课程的全部学生的学号和姓名；

SELECT sid,sname 
FROM (SELECT student_id FROM score GROUP BY student_id HAVING count(student_id)=1) AS B
LEFT JOIN student ON student.sid=B.student_id

24、查询男生、女生的人数；

SELECT gender,count(1) FROM student GROUP BY gender

 25、查询姓“张”的学生名单；

SELECT * FROM student WHERE sname LIKE '张%'

28、查询平均成绩大于85的所有学生的学号、姓名和平均成绩；

SELECT student_id,sname,avg(num) FROM score 
LEFT JOIN  student ON score.student_id=student.sid
GROUP BY student_id HAVING avg(num)>85

29、查询课程名称为“美术”，且分数低于60的学生姓名和分数；

SELECT sname,num FROM score
LEFT JOIN course ON course.cid=score.course_id
LEFT JOIN student ON student.sid=score.student_id
WHERE cname='美术' AND num<60

30、查询课程编号为003且课程成绩在80分以上的学生的学号和姓名；

SELECT student_id,sname FROM score LEFT JOIN student ON student.sid=score.student_id
WHERE course_id=3 AND num>80;

31、求选了课程的学生人数;

select count(distinct student_id) as 人数 from score;
 
select count(c) from (select count(student_id) as c from score group by student_id) as A;

32、查询选修“张磊”老师所授课程的学生中，成绩最高的学生姓名及其成绩；

select sname,num from score
left join student on score.student_id = student.sid
where score.course_id in 
	(select course.cid from course 
			left join teacher on course.teacher_id = teacher.tid where tname='张磊老师') 
				order by num desc limit 1;

SELECT sname,num FROM score
LEFT JOIN student ON score.student_id = student.sid
LEFT JOIN course ON score.course_id = course.cid
LEFT JOIN teacher ON course.teacher_id = teacher.tid
WHERE tname = '张磊老师'
ORDER BY num DESC LIMIT 1;

34、查询不同课程但成绩相同的学生的学号、课程号、学生成绩；

SELECT A1.student_id,A1.course_id,A2.course_id,A1.num,A2.num 
FROM score AS A1 ,score AS A2
 WHERE A1.course_id!=A2.course_id AND A1.num=A2.num
 GROUP BY student_id

36、检索至少选修两门课程的学生学号；

SELECT sid,sname 
FROM (SELECT student_id FROM score GROUP BY student_id HAVING count(student_id)>1) AS A  
LEFT JOIN student ON student.sid=A.student_id

37、查询全部学生都选修的课程的课程号和课程名；

SELECT cid,cname,count(course_id) FROM score
LEFT JOIN course ON score.course_id=course.cid
GROUP BY course_id 
HAVING count(course_id)=(SELECT count(1) FROM student);

38、查询没学过“张磊”老师讲授的任一门课程的学生姓名；

SELECT student_id,student.sname FROM score
LEFT JOIN student ON score.student_id=student.sid
WHERE score.course_id NOT IN
(SELECT cid FROM course LEFT JOIN teacher ON course.teacher_id=teacher.tid WHERE tname='张磊老师')
GROUP BY student_id

39、查询两门以上不及格课程的同学的学号及其平均成绩；

 SELECT s1.student_id,
	(SELECT avg(num) FROM score AS s2 WHERE s2.student_id = s1.student_id) as 平均成绩
 FROM score AS s1 WHERE num < 60
 GROUP BY student_id
 HAVING COUNT(student_id) > 1;

40、检索“004”课程分数小于60，按分数降序排列的同学学号；

SELECT student_id FROM score WHERE course_id=4 AND num<60 ORDER BY num DESC;

41、删除“002”同学的“001”课程的成绩；

 delete from score where course_id = 1 and student_id = 2