mysql进阶练习

一 .  MySQL进阶练习

/*==========================创建班级表=============================*/
CREATE TABLE class (
  cid int(11) NOT NULL AUTO_INCREMENT,
  class_name varchar(32) NOT NULL,
  PRIMARY KEY (cid)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;

 INSERT INTO class(cid,class_name) VALUES
                     (1,"三级二班"),
                     (2,"三级三班"),
                     (3,"一级二班"),
                     (4,"二级九班");

/*创建教师信息表*/
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;
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");

/*========================创建课程信息表=============================*/
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);

/*=====================创建学生信息表================================*/
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;
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“);

 /*=====================创建学生成绩信息表=========================*/
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;
INSERT INTO `score` VALUES ('', '', '', ''), ('', '', '', ''),
('', '', '', ''), ('', '', '', ''),
('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', ''), ('', '', '', ''),
 ('', '', '', '');

 /*===================练习题目=====================*/
 sql执行顺序:(1)FROM--(2)--ON <join_condition>--(3)<join_type> JOIN <right_table>
 --(4)WHERE <where_condition>--(5)GROUP BY <group_by_list>--(6)HAVING <having_condition>
 --(7)SELECT --(8)DISTINCT <select_list>--(9)ORDER BY <order_by_condition>--(10)LIMIT <limit_number>

1、查询所有的课程的名称以及对应的任课老师姓名
(way1.)
select
    course.cname,teacher.tname
from
    course,teacher
where
    teacher.tid=course.teacher_id;
(way2.)
SELECT
    course.cname,
    teacher.tname
FROM
    course
INNER JOIN teacher ON course.teacher_id = teacher.tid;

2、查询学生表中男女生各有多少人
(way1.)
select
    count(student.gender)
from
    student where student.gender="男";
select
    count(student.gender)
from
    student where student.gender="女";
(way2.)
SELECT
    gender as 性别,
    count(1) as 人数
FROM
    student
GROUP BY
    gender;

3、查询物理成绩等于100的学生的姓名
(way1.)
SELECT
    student.sname
FROM
    student
WHERE
    sid IN (
        SELECT
            student_id
        FROM
            score
        INNER JOIN course ON score.course_id = course.cid
        WHERE
            course.cname = '物理'
        AND score.num = 100
    );
(way2.)
select
    student.sname
from
    student
where
    sid in (select
                student_id
            from
                  score
            where score.num=100 and score.course_id=2);

4、查询平均成绩大于八十分的同学的姓名和平均成绩

select student.sname,score_avg.avg_num
from
    student,
     (
            select
                student_id,avg(score.num) AS avg_num
            from
                score
            group by
                score.student_id
            having avg(score.num)>80
            ) AS score_avg
WHERE student.sid=score_avg.student_id;

(way2.)
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;

5、查询所有学生的学号，姓名，选课数，总成绩
(way1.)
SELECT
    student.sid,
    student.sname,
    t2.course_num,
    t2.total_num
FROM
    student
LEFT JOIN (
    SELECT
        student_id,
        COUNT(course_id) course_num,
        sum(num) total_num
    FROM
        score
    GROUP BY
        student_id
)AS t2
ON student.sid = t2.student_id;

6、 查询姓李老师的个数
SELECT COUNT(tid)
FROM teacher
WHERE tname LIKE "李%";

7、 查询没有报李平老师课的学生姓名
(way1.)
SELECT sname
FROM student
WHERE student.sid
NOT IN (SELECT DISTINCT student_id  /*DISTINCT筛选不重复的记录*/
    FROM score
    WHERE course_id=2 OR course_id=4
    );
(way2.)
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、 查询物理课程比生物课程高的学生的学号
(way1.)
SELECT
  table1.student_id
FROM
  (
      SELECT
          student_id,num
      AS
          subject_num
      FROM
          score
      WHERE
          course_id=2
  ) AS table1
INNER JOIN
  (
      SELECT
          student_id,num
      AS
          biology_num
      FROM
          score
      WHERE
          course_id=1
 ) AS table2
 ON
    table1.student_id=table2.student_id
 WHERE
    table1.subject_num>table2.biology_num;

(way2.)
SELECT
    t1.student_id
FROM
    (
        SELECT
            student_id,
            num
        FROM
            score
        WHERE
            course_id = (
                SELECT
                    cid
                FROM
                    course
                WHERE
                    cname = '物理'
            )
    ) AS t1
INNER JOIN (
    SELECT
        student_id,
        num
    FROM
        score
    WHERE
        course_id = (
            SELECT
                cid
            FROM
                course
            WHERE
                cname = '生物'
        )
) AS t2 ON t1.student_id = t2.student_id
WHERE
    t1.num > t2.num;

9、 查询没有同时选修物理课程和体育课程的学生姓名
(way1.)
SELECT
  sname
FROM
  student
WHERE
  sid NOT IN
      (
          SELECT
              t1.student_id
          FROM
              (
                  SELECT
                      student_id,course_id
                  FROM
                      score
                  WHERE
                      course_id
                  IN (
                        SELECT
                            cid
                        FROM
                            course
                        WHERE
                            cname="物理"
                      )

               ) AS t1
              INNER JOIN
              (
                  SELECT
                      student_id,course_id
                  FROM
                      score
                  WHERE
                      course_id
                  IN (
                        SELECT
                            cid
                        FROM
                            course
                        WHERE
                            cname="体育"
                      )

               ) AS t2
              ON t1.student_id=t2.student_id
      );

(way2.)
思路(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)
SELECT
    student.sname
FROM
    student
WHERE
    sid IN (
        SELECT
            student_id
        FROM
            score
        WHERE
            course_id IN (
                SELECT
                    cid
                FROM
                    course
                WHERE
                    cname = '物理'
                OR cname = '体育'
            )
        GROUP BY
            student_id
        HAVING
            COUNT(course_id) = 1
    );

10、查询挂科超过两门(包括两门)的学生姓名和班级
(way1.)
SELECT
    class_name,t1.sname
FROM
    class
INNER JOIN (
        SELECT
            sname,class_id
        FROM
            student
        WHERE
        sid IN
           (
               SELECT
                  student_id
               FROM
                  score
               WHERE
                  score.num<60
               GROUP BY
                  student_id
                HAVING COUNT(num)=2
           )
       )AS t1 ON class.cid=t1.class_id;

(way2.)思路求出<60的表，然后对学生进行分组，统计课程数目>=2
    SELECT
    student.sname,
    class.class_name
FROM
    student
INNER JOIN (
    SELECT
        student_id
    FROM
        score
    WHERE
        num < 60
    GROUP BY
        student_id
    HAVING
        count(course_id) >= 2
) AS t1
INNER JOIN class ON student.sid = t1.student_id
AND student.class_id = class.cid;

11、查询选修了所有课程的学生姓名
(way1.)
select
    student.sname
from
    student
where
    sid in
        (
            select
                student_id
            from
                score
            group by
                student_id
            having
                count(course_id)=4
        );
(way2.)
SELECT
    student.sname
FROM
    student
WHERE
    sid IN (
        SELECT
            student_id
        FROM
            score
        GROUP BY
            student_id
        HAVING
            COUNT(course_id) = (SELECT count(cid) FROM course)
    );

12、查询李平老师教的课程的所有成绩记录
(way1.)
select
    course_id,num
from
    score
where
    score.course_id in
        (
            select
                cid
            from
                course
            inner join
                teacher
            on
                course.teacher_id=teacher.tid
            where
                teacher.tname="李平老师"
        );
(way2.)
SELECT
    *
FROM
    score
WHERE
    course_id IN (
        SELECT
            cid
        FROM
            course
        INNER JOIN teacher ON course.teacher_id = teacher.tid
        WHERE
            teacher.tname = '李平老师'
    );
13、查询全部学生都选修了的课程号和课程名
（way1.)
select
    cid,cname
from
    course
where
    cid in
        (
            select
                course_id
            from
                score
            group by
                course_id
            having count(student_id)= (select count(sid) from student)
        );
(way2.)
SELECT
    cid,
    cname
FROM
    course
WHERE
    cid IN (
        SELECT
            course_id
        FROM
            score
        GROUP BY
            course_id
        HAVING
            COUNT(student_id) = (
                SELECT
                    COUNT(sid)
                FROM
                    student
            )
    );

14、查询每门课程被选修的次数
(way1.)
select
    course_id,count(student_id)
from
    score
group by
    course_id;

15、查询只选修了一门课程的学生姓名和学号
select
    sid,sname
from
    student
where
    sid in
    (
        select
            student_id
        from
            score
        group by
            student_id
        having
            count(course_id)=1
    );

16、查询所有学生考出的总成绩并按从高到低排序（成绩去重）
(way1.)
select
    sid,sname,t1.num
from
    student
left join
    (
        select
            student_id,sum(score.num) as num
        from
            score
        group by
            student_id
      ) as t1 on student.sid=t1.student_id
order by t1.num desc;

17、查询平均成绩大于85的学生姓名和平均成绩
select
    sname,t1.num
from
    student
inner join
    (
        select
            student_id,avg(num) as num
        from
            score
        group by
            student_id
        having
            avg(num)>85
    ) as t1 on student.sid=t1.student_id;

18、查询生物成绩不及格的学生姓名和对应生物分数
(way1.)
select
    sname,t1.num
from
    student
inner join
    (
        select
           student_id,num
        from
            score
        where
            course_id=(select cid from course where cname="生物") and num<60
    )as t1 on student.sid=t1.student_id;
(way2.)
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
    course.cname = '生物'
AND score.num < 60;

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
(way1.)
select
    sname
from
    student
where
    sid in
        (
            select
                t1.student_id
            from
                (
                    select
                        student_id,num
                    from
                        score
                    where
                        course_id in
                             (
                                select
                                    cid
                                from
                                    course
                                where
                                    course.teacher_id=(select tid from teacher where tname="李平老师")
                             )
                    group by student_id
                    order by
                        AVG(num) DESC
                    limit 1
                )as t1
       );

(way2.)
SELECT
    sname
FROM
    student
WHERE
    sid = (
        SELECT
            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'
            )
        GROUP BY
            student_id
        ORDER BY
            AVG(num) DESC
        LIMIT 1
    );

20、查询每门课程成绩最好的前两名学生姓名
SELECT
    *
FROM
    score
ORDER BY
    course_id,
    num DESC;

#表1：求出每门课程的课程course_id,与最高分数first_num
SELECT
    course_id,
    max(num) first_num
FROM
    score
GROUP BY
    course_id;

#表2：去掉最高分，再按照课程分组，取得的最高分，就是第二高的分数second_num
SELECT
    score.course_id,
    max(num) second_num
FROM
    score
INNER JOIN (
    SELECT
        course_id,
        max(num) first_num
    FROM
        score
    GROUP BY
        course_id
) AS t ON score.course_id = t.course_id
WHERE
    score.num < t.first_num
GROUP BY
    course_id;

#将表1和表2联合到一起，得到一张表t3，包含课程course_id与该们课程的first_num与second_num
SELECT
    t1.course_id,
    t1.first_num,
    t2.second_num
FROM
    (
        SELECT
            course_id,
            max(num) first_num
        FROM
            score
        GROUP BY
            course_id
    ) AS t1
INNER JOIN (
    SELECT
        score.course_id,
        max(num) second_num
    FROM
        score
    INNER JOIN (
        SELECT
            course_id,
            max(num) first_num
        FROM
            score
        GROUP BY
            course_id
    ) AS t ON score.course_id = t.course_id
    WHERE
        score.num < t.first_num
    GROUP BY
        course_id
) AS t2 ON t1.course_id = t2.course_id;

#查询前两名的学生（有可能出现并列第一或者并列第二的情况）
SELECT
    score.student_id,
    t3.course_id,
    t3.first_num,
    t3.second_num
FROM
    score
INNER JOIN (
    SELECT
        t1.course_id,
        t1.first_num,
        t2.second_num
    FROM
        (
            SELECT
                course_id,
                max(num) first_num
            FROM
                score
            GROUP BY
                course_id
        ) AS t1
    INNER JOIN (
        SELECT
            score.course_id,
            max(num) second_num
        FROM
            score
        INNER JOIN (
            SELECT
                course_id,
                max(num) first_num
            FROM
                score
            GROUP BY
                course_id
        ) AS t ON score.course_id = t.course_id
        WHERE
            score.num < t.first_num
        GROUP BY
            course_id
    ) AS t2 ON t1.course_id = t2.course_id
) AS t3 ON score.course_id = t3.course_id
WHERE
    score.num >= t3.second_num
AND score.num <= t3.first_num;

#排序后可以看的明显点
SELECT
    score.student_id,
    t3.course_id,
    t3.first_num,
    t3.second_num
FROM
    score
INNER JOIN (
    SELECT
        t1.course_id,
        t1.first_num,
        t2.second_num
    FROM
        (
            SELECT
                course_id,
                max(num) first_num
            FROM
                score
            GROUP BY
                course_id
        ) AS t1
    INNER JOIN (
        SELECT
            score.course_id,
            max(num) second_num
        FROM
            score
        INNER JOIN (
            SELECT
                course_id,
                max(num) first_num
            FROM
                score
            GROUP BY
                course_id
        ) AS t ON score.course_id = t.course_id
        WHERE
            score.num < t.first_num
        GROUP BY
            course_id
    ) AS t2 ON t1.course_id = t2.course_id
) AS t3 ON score.course_id = t3.course_id
WHERE
    score.num >= t3.second_num
AND score.num <= t3.first_num
ORDER BY
    course_id;

#可以用以下命令验证上述查询的正确性
SELECT
    *
FROM
    score
ORDER BY
    course_id,
    num DESC;