MYSQL 练习

导出现有数据库数据：

• 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

导入现有数据库数据：

• mysqldump -uroot -p密码  数据库名称 < 文件路径

一、表关系

请创建如下表，并创建相关约束

二、操作表

1、自行创建测试数据

/*
Navicat MySQL Data Transfer

Source Server         : abc
Source Server Version : 50713
Source Host           : localhost:3306
Source Database       : lx

Target Server Type    : MYSQL
Target Server Version : 50713
File Encoding         : 65001

Date: 2016-10-24 18:07:25
*/

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(20) DEFAULT NULL,
  PRIMARY KEY (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of class
-- ----------------------------
INSERT INTO `class` VALUES ('', '三年二班');
INSERT INTO `class` VALUES ('', '一年三班');
INSERT INTO `class` VALUES ('', '三年一班');
INSERT INTO `class` VALUES ('', 'python 二期');

-- ----------------------------
-- Table structure for `course`
-- ----------------------------
DROP TABLE IF EXISTS `course`;
CREATE TABLE `course` (
  `cid` int(11) NOT NULL AUTO_INCREMENT,
  `cname` varchar(20) DEFAULT NULL,
  `teache_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`cid`),
  KEY `fk_c_t` (`teache_id`),
  CONSTRAINT `fk_c_t` FOREIGN KEY (`teache_id`) REFERENCES `teacher` (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of course
-- ----------------------------
INSERT INTO `course` VALUES ('', '生物', '');
INSERT INTO `course` VALUES ('', '体育', '');
INSERT INTO `course` VALUES ('', '物理', '');

-- ----------------------------
-- Table structure for `score`
-- ----------------------------
DROP TABLE IF EXISTS `score`;
CREATE TABLE `score` (
  `sid` int(11) NOT NULL AUTO_INCREMENT,
  `student_id` int(11) DEFAULT NULL,
  `corse_id` int(11) DEFAULT NULL,
  `number` int(11) DEFAULT NULL,
  PRIMARY KEY (`sid`),
  KEY `fk_s_st` (`student_id`),
  KEY `fk_s_co` (`corse_id`),
  CONSTRAINT `fk_s_co` FOREIGN KEY (`corse_id`) REFERENCES `course` (`cid`),
  CONSTRAINT `fk_s_st` FOREIGN KEY (`student_id`) REFERENCES `student` (`sid`)
) ENGINE=InnoDB AUTO_INCREMENT=33 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of score
-- ----------------------------
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');
INSERT INTO `score` VALUES ('', '', '', '');

-- ----------------------------
-- Table structure for `student`
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
  `sid` int(11) NOT NULL AUTO_INCREMENT,
  `sname` varchar(20) DEFAULT NULL,
  `gender` varchar(12) DEFAULT NULL,
  `class_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`sid`),
  KEY `fk_s_c` (`class_id`),
  CONSTRAINT `fk_s_c` FOREIGN KEY (`class_id`) REFERENCES `class` (`cid`)
) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES ('', '钢蛋', '女', '');
INSERT INTO `student` VALUES ('', '铁锤', '女', '');
INSERT INTO `student` VALUES ('', '山炮', '男', '');
INSERT INTO `student` VALUES ('', '张三', '男', '');
INSERT INTO `student` VALUES ('', '李四', '男', '');
INSERT INTO `student` VALUES ('', '王五', '男', '');
INSERT INTO `student` VALUES ('', '马六', '女', '');
INSERT INTO `student` VALUES ('', '霍七', '男', '');
INSERT INTO `student` VALUES ('', '贺八', '男', '');

-- ----------------------------
-- Table structure for `teacher`
-- ----------------------------
DROP TABLE IF EXISTS `teacher`;
CREATE TABLE `teacher` (
  `tid` int(11) NOT NULL AUTO_INCREMENT,
  `tname` varchar(20) DEFAULT NULL,
  PRIMARY KEY (`tid`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of teacher
-- ----------------------------
INSERT INTO `teacher` VALUES ('', '波多');
INSERT INTO `teacher` VALUES ('', '苍空');
INSERT INTO `teacher` VALUES ('', '饭岛');

创建表（结构）

2、查询“生物”课程比“物理”课程成绩高的所有学生的学号；

思路：

    获取所有有生物课程的人（学号，成绩） - 临时表

    获取所有有物理课程的人（学号，成绩） - 临时表

    根据【学号】连接两个临时表：

        学号 物理成绩 生物成绩       然后再进行筛选

select A.student_id,生物,物理 from

        (select student_id,number as 生物 from score left join course on score.corse_id = course.cid where course.cname = '生物') as A

        left join

        (select student_id,number  as 物理 from score left join course on score.corse_id = course.cid where course.cname = '物理') as B

        on A.student_id = B.student_id where 物理 >  生物 ;       

 

3、查询平均成绩大于60分的同学的学号和平均成绩；

    思路：

        根据学生分组，使用avg获取平均值，通过having对avg进行筛选      

select student_id,avg(number) from score GROUP BY student_id having avg(number)>60;

 

4、查询所有同学的学号、姓名、选课数、总成绩；

SELECT
    score.student_id,
    COUNT(score.corse_id),
    SUM(score.number),
    student.sname
FROM
    score
LEFT JOIN student ON student.sid = score.student_id
GROUP BY
    student_id

 

5、查询姓“李”的老师的个数

    

select COUNT(tid) from teacher where tname LIKE"波%";

select count(1) from (select tid from teacher where tname like '波%') as B

6、查询没学过“叶平”老师课的同学的学号、姓名；

    思路：

        先查到“叶平老师”老师教的所有课ID

        获取选过课的所有学生ID

        学生表中筛选 

select * from student where sid not in(
select student_id from score WHERE score.corse_id in(
select cid from course
LEFT JOIN teacher on teacher.tid = course.teache_id where teacher.tname = "波多"
)
)

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001又选择002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，两门均已选择

 select student_id,sname from

    (select student_id,corse_id from score where corse_id = 1 or corse_id = 2) as B

    left join student on B.student_id = student.sid group by student_id HAVING count(student_id) = 2

8、查询学过“叶平”老师所教的所有课的同学的学号、姓名； 

select * from student where sid  in(
select student_id from score WHERE score.corse_id in(
select cid from course
LEFT JOIN teacher on teacher.tid = course.teache_id where teacher.tname = "波多"
)
)

9、查询课程编号“002”的成绩比课程编号“001”课程低的所有同学的学号、姓名；

    

select c.student_id,student.sname from
(select A.student_id,a,b from

        (select student_id,number as a from score left join course on score.corse_id = course.cid where course.cid = 1) as A

        left join

        (select student_id,number  as b from score left join course on score.corse_id = course.cid where course.cid = 2) as B
        on A.student_id = B.student_id where b >  a ) as c
         LEFT JOIN
       student on c.student_id = student.sid;

10、查询有课程成绩小于60分的同学的学号、姓名；  

select sid,sname from student where sid in (
        select distinct student_id from score where number < 60
    )

select sid,sname from student where sid in (
        select  student_id from score where number < 60 GROUP BY student_id
    )

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(corse_id) = (select count(cid) from course)
 

12、查询至少有一门课与学号为“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，获取所有学生信息

        再与学生表连接，获取姓名

select student_id,sname, count(corse_id)
        from score left join student on score.student_id = student.sid
        where student_id != 1 and corse_id in (select corse_id from score where student_id = 1) group by student_id

13、查询至少学过学号为“001”同学所有课的其他同学学号和姓名；

        先找到和001的学过的所有人

        然后个数 ＝ 001所有学科     ＝＝》 其他人可能选择的更多

 select student_id,sname, count(corse_id)
        from score left join student on score.student_id = student.sid
        where student_id != 1 and corse_id in (select corse_id from score where student_id = 1)
group by student_id

14、查询和“002”号的同学学习的课程完全相同的其他同学学号和姓名；

         

        个数相同

        002学过的也学过

select student_id,sname from score left join student on score.student_id = student.sid where student_id in (
            select student_id from score  where student_id != 1 group by student_id HAVING count(corse_id) = (select count(1) from score where student_id = 1)
        ) and corse_id in (select corse_id from score where student_id = 1) group by student_id HAVING count(corse_id) = (select count(1) from score where student_id = 1)

15、删除学习“叶平”老师课的score表记录；  

delete from score where corse_id in (
        select cid from course left join teacher on course.teache_id = teacher.tid where teacher.tname = '饭岛'
    )

16、向SC表中插入一些记录，这些记录要求符合以下条件：①没有上过编号“002”课程的同学学号；②插入“002”号课程的平均成绩；

  

insert into score(student_id, corse_id, number) select sid,2,(select avg(number) from score where corse_id = 2)
    from student where sid not in (
        select student_id from score where corse_id = 2
    )
     

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,有效课程数,有效平均分；

   

 select sc.student_id,
        (select number from score left join course on score.corse_id = course.cid where course.cname = "生物" and score.student_id=sc.student_id) as sy,
        (select number from score left join course on score.corse_id = course.cid where course.cname = "物理" and score.student_id=sc.student_id) as wl,
        (select number from score left join course on score.corse_id = course.cid where course.cname = "体育" and score.student_id=sc.student_id) as ty,
        count(sc.corse_id),
        avg(sc.number)
    from score as sc
    group by student_id desc  

 select student_id,
        (select number from score as a WHERE a.student_id=b.student_id and  corse_id=1)as sw,
        (select number from score as a WHERE a.student_id=b.student_id and corse_id=2) as ty,
         (select number from score as a WHERE a.student_id=b.student_id  and corse_id=3) as wl,
        count(corse_id),avg(number)from score as b group by student_id ORDER BY avg(number) desc 

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 corse_id, max(number) as max_num, min(number) as min_num from score group by corse_id;

19、按各科平均成绩从低到高和及格率的百分数从高到低顺序；

    思路：case when .. then   (类似三目（元）运算)   

select corse_id, avg(number) ,sum(case when score.number > 60 then 1 else 0 END)/count(1)*100 as percent
from score group by corse_id order by avg(number) asc,percent desc;

20、课程平均分从高到低显示（现实任课老师）； 

select avg(if(isnull(score.number),0,score.number)),teacher.tname from course
    left join score on course.cid = score.corse_id
    left join teacher on course.teache_id = teacher.tid

    group by score.corse_id

select avg(score.number),teacher.tname from course
    left join score on course.cid = score.corse_id
    left join teacher on course.teache_id = teacher.tid

    group by score.corse_id

21、查询各科成绩前三名的记录:(不考虑成绩并列情况)

 select score.sid,score.corse_id,score.number,T.first_num,T.second_num from score left join
    (
    select sid,
        (select number from score as s2 where s2.corse_id = s1.corse_id order by number desc limit 0,1) as first_num,
        (select number from score as s2 where s2.corse_id = s1.corse_id order by number desc limit 2,1) as second_num
    from
        score as s1
    ) as T
    on score.sid =T.sid
    where score.number <= T.first_num and score.number >= T.second_num

22、查询每门课程被选修的学生数；  

select corse_id, count(1) from score group by corse_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 student.sid, student.sname, count(1) from score

    left join student on score.student_id  = student.sid

     group by corse_id having count(1) = 1

24、查询男生、女生的人数；

    

select * from
    (select count(1) as man from student where gender='男')as A ,
    (select count(1) as feman from student where gender='女') as B

25、查询姓“张”的学生名单；  

select sname from student where sname like '张%';

26、查询同名同姓学生名单，并统计同名人数；  

select sname,count(1) as count from student group by sname;

27、查询每门课程的平均成绩，结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列；   

select corse_id,avg(if(isnull(number), 0 ,number)) as avg from score group by corse_id order by avg asc,corse_id desc;

select corse_id,avg(number)from score group by corse_id order by avg(number) asc,corse_id desc;

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,avg(number),student.sname FROM score LEFT JOIN student on student.sid = score.student_id GROUP BY student_id
HAVING avg(number)>85;

29、查询课程名称为“数学”，且分数低于60的学生姓名和分数； 

SELECT student.sname,score.number FROM score LEFT JOIN student on student.sid = score.student_id left join course on score.corse_id = course.cid
WHERE score.number<60 and course.cname= "物理"

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.sname,score.student_id from score LEFT JOIN student
on student.sid = score.student_id WHERE score.number>80 and score.corse_id=3 GROUP BY student_id 

31、求选了课程的学生人数 

select count(distinct student_id) 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“杨艳”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,number from score
    left join student on score.student_id = student.sid
    where score.corse_id in (select course.cid from course left join teacher
        on course.teache_id = teacher.tid where tname='波多') order by number desc limit ;

33、查询各个课程及相应的选修人数；

select course.cname,count() from score
    left join course on score.corse_id = course.cid
    group by corse_id;

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 DISTINCT s1.corse_id,s2.corse_id,s1.number,s2.number from score as s1, score as s2 where s1.number = s2.number and s1.corse_id != s2.corse_id;

35、查询每门课程成绩最好的前两名；

select score.sid,score.corse_id,score.number,T.first_num,T.second_num from score left join
    (
    select
        sid,
        (select number from score as s2 where s2.corse_id = s1.corse_id order by number desc limit ,) as first_num,
        (select number from score as s2 where s2.corse_id = s1.corse_id order by number desc limit ,) as second_num
    from
        score as s1
    ) as T
    on score.sid =T.sid
    where score.number <= T.first_num and score.number >= T.second_num

36、检索至少选修两门课程的学生学号；

 select student_id from score group by student_id having count(student_id) > 1

37、查询全部学生都选修的课程的课程号和课程名；  

select  corse_id,course.cname,count(student_id) from score LEFT JOIN course on
score.corse_id = course.cid GROUP BY corse_id HAVING COUNT(student_id)=(select count(sid) FROM student)

38、查询没学过“叶平”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.corse_id not in (
        select cid from course left join teacher on course.teache_id = teacher.tid where tname = '波多'
    )
    group by student_id

select student_id,student.sname from score
    left join student on score.student_id = student.sid
    where score.corse_id not in (
        select cid from course left join teacher on course.teache_id = teacher.tid where tname = '波多'
    )
    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 student_id,avg(number) from score  where number<60 GROUP BY student_id having count(corse_id)>=2

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,number from score where corse_id=4 and number<60 ORDER BY number desc

41、删除“002”同学的“001”课程的成绩； 

 delete from score where corse_id = 1 and student_id = 2