MySQL作业三（MySQL练习50题）

 Student(SId,Sname,Sage,Ssex)
 --SId 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别

mysql> create table Student(
    -> Sid int auto_increment primary key,
    -> Sname varchar(255) not null,
    -> Sage date not null,
    -> Ssex enum('男', '女') not null
    -> );
Query OK, 0 rows affected (0.04 sec)

mysql> desc Student;
+-------+-----------------+------+-----+---------+----------------+
| Field | Type            | Null | Key | Default | Extra          |
+-------+-----------------+------+-----+---------+----------------+
| Sid   | int             | NO   | PRI | NULL    | auto_increment |
| Sname | varchar(255)    | NO   |     | NULL    |                |
| Sage  | date            | NO   |     | NULL    |                |
| Ssex  | enum('男','女') | NO   |     | NULL    |                |
+-------+-----------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

2）课程表

 Course(CId,Cname,TId)
 --CId 课程编号,Cname 课程名称,TId 教师编号（先创建教师表）
mysql> CREATE TABLE Course (
    ->     CId INT AUTO_INCREMENT PRIMARY KEY,
    ->     Cname VARCHAR(255) NOT NULL,
    ->     TId INT,
    ->     FOREIGN KEY (TId) REFERENCES Teacher(TId)
    -> );
Query OK, 0 rows affected (0.02 sec)

mysql> desc Course;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| CId   | int          | NO   | PRI | NULL    | auto_increment |
| Cname | varchar(255) | NO   |     | NULL    |                |
| TId   | int          | YES  | MUL | NULL    |                |
+-------+--------------+------+-----+---------+----------------+
3 rows in set (0.00 sec)

3）教师表

Teacher(TId,Tname)
 --TId 教师编号,Tname 教师姓名
mysql> CREATE TABLE Teacher (
    ->     TId INT AUTO_INCREMENT PRIMARY KEY,
    ->     Tname VARCHAR(255) NOT NULL
    -> );
Query OK, 0 rows affected (0.01 sec)

mysql> desc Teacher;
+-------+--------------+------+-----+---------+----------------+
| Field | Type         | Null | Key | Default | Extra          |
+-------+--------------+------+-----+---------+----------------+
| TId   | int          | NO   | PRI | NULL    | auto_increment |
| Tname | varchar(255) | NO   |     | NULL    |                |
+-------+--------------+------+-----+---------+----------------+
2 rows in set (0.00 sec)

4）成绩表

SC(SId,CId,score)
 --SId 学生编号,CId 课程编号,score 分数
mysql> CREATE TABLE SC (
    ->     SId INT,
    ->     CId INT,
    ->     score DECIMAL(5, 2),
    ->     PRIMARY KEY (SId, CId),
    ->     FOREIGN KEY (SId) REFERENCES Student(SId),
    ->     FOREIGN KEY (CId) REFERENCES Course(CId)
    -> );
Query OK, 0 rows affected (0.02 sec)

mysql> desc SC;
+-------+--------------+------+-----+---------+-------+
| Field | Type         | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| SId   | int          | NO   | PRI | NULL    |       |
| CId   | int          | NO   | PRI | NULL    |       |
| score | decimal(5,2) | YES  |     | NULL    |       |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)

2、插入数据

1）学生Student

insert into Student values('01' , '赵雷' , '1990-01-01' , '男');
insert into Student values('02' , '钱电' , '1990-12-21' , '男');
insert into Student values('03' , '孙风' , '1990-12-20' , '男');
insert into Student values('04' , '李云' , '1990-12-06' , '男');
insert into Student values('05' , '周梅' , '1991-12-01' , '女');
insert into Student values('06' , '吴兰' , '1992-01-01' , '女');
insert into Student values('07' , '郑竹' , '1989-01-01' , '女');
insert into Student values('09' , '张三' , '2017-12-20' , '女');
insert into Student values('10' , '李四' , '2017-12-25' , '女');
insert into Student values('11' , '李四' , '2012-06-06' , '女');
insert into Student values('12' , '赵六' , '2013-06-13' , '女');
insert into Student values('13' , '孙七' , '2014-06-01' , '女');

mysql> select * from Student;
+-----+-------+------------+------+|
 Sid | Sname | Sage       | Ssex |
+-----+-------+------------+------+
|   1 | 赵雷  | 1990-01-01 | 男   |
|   2 | 钱电  | 1990-12-21 | 男   |
|   3 | 孙风  | 1990-12-20 | 男   |
|   4 | 李云  | 1990-12-06 | 男   |
|   5 | 周梅  | 1991-12-01 | 女   |
|   6 | 吴兰  | 1992-01-01 | 女   |
|   7 | 郑竹  | 1989-01-01 | 女   |
|   9 | 张三  | 2017-12-20 | 女   |
|  10 | 李四  | 2017-12-25 | 女   |
|  11 | 李四  | 2012-06-06 | 女   |
|  12 | 赵六  | 2013-06-13 | 女   |
|  13 | 孙七  | 2014-06-01 | 女   |
+-----+-------+------------+------+
12 rows in set (0.00 sec)

2）科目表Course

insert into Course values('01' , '语文' , '02');
insert into Course values('02' , '数学' , '01');
insert into Course values('03' , '英语' , '03');
mysql> select * from Course;
+-----+-------+------+
| CId | Cname | TId  |
+-----+-------+------+
|   1 | 语文  |    2 |
|   2 | 数学  |    1 |
|   3 | 英语  |    3 |
+-----+-------+------+
3 rows in set (0.00 sec)

3）教师表 Teacher

insert into Teacher values('01' , '张三');
insert into Teacher values('02' , '李四');
insert into Teacher values('03' , '王五');
mysql> select * from Teacher;
+-----+-------+
| TId | Tname |
+-----+-------+
|   1 | 张三  |
|   2 | 李四  |
|   3 | 王五  |
+-----+-------+
3 rows in set (0.00 sec)

4）成绩表 SC

insert into SC values('01' , '01' , 80);
insert into SC values('01' , '02' , 90);
insert into SC values('01' , '03' , 99);
insert into SC values('02' , '01' , 70);
insert into SC values('02' , '02' , 60);
insert into SC values('02' , '03' , 80);
insert into SC values('03' , '01' , 80);
insert into SC values('03' , '02' , 80);
insert into SC values('03' , '03' , 80);
insert into SC values('04' , '01' , 50);
insert into SC values('04' , '02' , 30);
insert into SC values('04' , '03' , 20);
insert into SC values('05' , '01' , 76);
insert into SC values('05' , '02' , 87);
insert into SC values('06' , '01' , 31);
insert into SC values('06' , '03' , 34);
insert into SC values('07' , '02' , 89);
insert into SC values('07' , '03' , 98);
mysql> select * from SC;
+-----+-----+-------+
| SId | CId | score |
+-----+-----+-------+
|   1 |   1 | 80.00 |
|   1 |   2 | 90.00 |
|   1 |   3 | 99.00 |
|   2 |   1 | 70.00 |
|   2 |   2 | 60.00 |
|   2 |   3 | 80.00 |
|   3 |   1 | 80.00 |
|   3 |   2 | 80.00 |
|   3 |   3 | 80.00 |
|   4 |   1 | 50.00 |
|   4 |   2 | 30.00 |
|   4 |   3 | 20.00 |
|   5 |   1 | 76.00 |
|   5 |   2 | 87.00 |
|   6 |   1 | 31.00 |
|   6 |   3 | 34.00 |
|   7 |   2 | 89.00 |
|   7 |   3 | 98.00 |
+-----+-----+-------+
18 rows in set (0.00 sec)

3、练习题目

1、查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数、

mysql> SELECT
    ->     s.*,
    ->     sc1.score AS score_01,
    ->     sc2.score AS score_02
    -> FROM
    ->     Student s
    -> JOIN
    ->     SC sc1 ON s.SId = sc1.SId AND sc1.CId = '01'
    -> JOIN
    ->     SC sc2 ON s.SId = sc2.SId AND sc2.CId = '02'
    -> WHERE
    ->     sc1.score > sc2.score;
+-----+-------+------------+------+----------+----------+
| Sid | Sname | Sage       | Ssex | score_01 | score_02 |
+-----+-------+------------+------+----------+----------+
|   2 | 钱电  | 1990-12-21 | 男   |    70.00 |    60.00 |
|   4 | 李云  | 1990-12-06 | 男   |    50.00 |    30.00 |
+-----+-------+------------+------+----------+----------+
2 rows in set (0.00 sec)

1.1、查询同时存在" 01 "课程和" 02 "课程的情况

mysql> SELECT
    ->     s.*,
    ->     sc1.score AS score_01,
    ->     sc2.score AS score_02
    -> FROM
    ->     Student s
    -> JOIN
    ->     SC sc1 ON s.SId = sc1.SId AND sc1.CId = '01'
    -> JOIN
    ->     SC sc2 ON s.SId = sc2.SId AND sc2.CId = '02';
+-----+-------+------------+------+----------+----------+
| Sid | Sname | Sage       | Ssex | score_01 | score_02 |
+-----+-------+------------+------+----------+----------+
|   1 | 赵雷  | 1990-01-01 | 男   |    80.00 |    90.00 |
|   2 | 钱电  | 1990-12-21 | 男   |    70.00 |    60.00 |
|   3 | 孙风  | 1990-12-20 | 男   |    80.00 |    80.00 |
|   4 | 李云  | 1990-12-06 | 男   |    50.00 |    30.00 |
|   5 | 周梅  | 1991-12-01 | 女   |    76.00 |    87.00 |
+-----+-------+------------+------+----------+----------+
5 rows in set (0.00 sec)

1.2、查询存在" 01 "课程但可能不存在" 02 "课程的情况(不存在时显示为 null )

mysql> SELECT
    ->     s.*,
    ->     sc1.score AS score_01,
    ->     sc2.score AS score_02
    -> FROM
    ->     Student s
    -> JOIN
    ->     SC sc1 ON s.SId = sc1.SId AND sc1.CId = '01'
    -> LEFT JOIN
    ->     SC sc2 ON s.SId = sc2.SId AND sc2.CId = '02';
+-----+-------+------------+------+----------+----------+
| Sid | Sname | Sage       | Ssex | score_01 | score_02 |
+-----+-------+------------+------+----------+----------+
|   1 | 赵雷  | 1990-01-01 | 男   |    80.00 |    90.00 |
|   2 | 钱电  | 1990-12-21 | 男   |    70.00 |    60.00 |
|   3 | 孙风  | 1990-12-20 | 男   |    80.00 |    80.00 |
|   4 | 李云  | 1990-12-06 | 男   |    50.00 |    30.00 |
|   5 | 周梅  | 1991-12-01 | 女   |    76.00 |    87.00 |
|   6 | 吴兰  | 1992-01-01 | 女   |    31.00 |     NULL |
+-----+-------+------------+------+----------+----------+
6 rows in set (0.00 sec)

1.3 、查询不存在" 01 "课程但存在" 02 "课程的情况

mysql> SELECT
    ->     s.*,
    ->     sc.score AS score_02
    -> FROM
    ->     Student s
    -> JOIN
    ->     SC sc ON s.SId = sc.SId AND sc.CId = '02'
    -> WHERE
    ->     s.SId NOT IN (SELECT SId FROM SC WHERE CId = '01');
+-----+-------+------------+------+----------+
| Sid | Sname | Sage       | Ssex | score_02 |
+-----+-------+------------+------+----------+
|   7 | 郑竹  | 1989-01-01 | 女   |    89.00 |
+-----+-------+------------+------+----------+
1 row in set (0.00 sec)

2、查询平均成绩大于等于 60 分的同学的学生编号和学生姓名和平均成绩

mysql> SELECT
    ->     s.SId,
    ->     s.Sname,
    ->     AVG(sc.score) AS avg_score
    -> FROM
    ->     Student s
    -> JOIN
    ->     SC sc ON s.SId = sc.SId
    -> GROUP BY
    ->     s.SId, s.Sname
    -> HAVING
    ->     AVG(sc.score) >= 60;
+-----+-------+-----------+
| SId | Sname | avg_score |
+-----+-------+-----------+
|   1 | 赵雷  | 89.666667 |
|   2 | 钱电  | 70.000000 |
|   3 | 孙风  | 80.000000 |
|   5 | 周梅  | 81.500000 |
|   7 | 郑竹  | 93.500000 |
+-----+-------+-----------+
5 rows in set (0.00 sec)

3、查询在 SC 表存在成绩的学生信息

mysql> SELECT DISTINCT s.*
    -> FROM Student s
    -> JOIN SC ON s.SId = SC.SId;
+-----+-------+------------+------+
| Sid | Sname | Sage       | Ssex |
+-----+-------+------------+------+
|   1 | 赵雷  | 1990-01-01 | 男   |
|   2 | 钱电  | 1990-12-21 | 男   |
|   3 | 孙风  | 1990-12-20 | 男   |
|   4 | 李云  | 1990-12-06 | 男   |
|   5 | 周梅  | 1991-12-01 | 女   |
|   6 | 吴兰  | 1992-01-01 | 女   |
|   7 | 郑竹  | 1989-01-01 | 女   |
+-----+-------+------------+------+
7 rows in set (0.00 sec)

4、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩(没成绩的显示为 null )

mysql> SELECT
    ->     s.SId,
    ->     s.Sname,
    ->     COUNT(sc.CId) AS course_count,
    ->     SUM(sc.score) AS total_score
    -> FROM
    ->     Student s
    -> LEFT JOIN
    ->     SC sc ON s.SId = sc.SId
    -> GROUP BY
    ->     s.SId, s.Sname;
+-----+-------+--------------+-------------+
| SId | Sname | course_count | total_score |
+-----+-------+--------------+-------------+
|   1 | 赵雷  |            3 |      269.00 |
|   2 | 钱电  |            3 |      210.00 |
|   3 | 孙风  |            3 |      240.00 |
|   4 | 李云  |            3 |      100.00 |
|   5 | 周梅  |            2 |      163.00 |
|   6 | 吴兰  |            2 |       65.00 |
|   7 | 郑竹  |            2 |      187.00 |
|   9 | 张三  |            0 |        NULL |
|  10 | 李四  |            0 |        NULL |
|  11 | 李四  |            0 |        NULL |
|  12 | 赵六  |            0 |        NULL |
|  13 | 孙七  |            0 |        NULL |
+-----+-------+--------------+-------------+
12 rows in set (0.00 sec)

4.1 、查有成绩的学生信息

mysql> SELECT DISTINCT s.* FROM
    -> Student s
    -> RIGHT JOIN SC sc
    -> ON s.Sid = sc.Sid;
+------+-------+------------+------+
| Sid  | Sname | Sage       | Ssex |
+------+-------+------------+------+
|    1 | 赵雷  | 1990-01-01 | 男   |
|    2 | 钱电  | 1990-12-21 | 男   |
|    3 | 孙风  | 1990-12-20 | 男   |
|    4 | 李云  | 1990-12-06 | 男   |
|    5 | 周梅  | 1991-12-01 | 女   |
|    6 | 吴兰  | 1992-01-01 | 女   |
|    7 | 郑竹  | 1989-01-01 | 女   |
+------+-------+------------+------+
7 rows in set (0.00 sec)

5、查询「李」姓老师的数量

mysql> select count(Tname) from Teacher group by Tname having Tname like"李%";
+--------------+
| count(Tname) |
+--------------+
|            1 |
+--------------+
1 row in set (0.00 sec)

6、查询学过「张三」老师授课的同学的信息

mysql> SELECT DISTINCT s.*
    -> FROM Student s
    -> JOIN SC sc ON s.SId = sc.SId
    -> JOIN Course c ON sc.CId = c.CId
    -> JOIN Teacher t ON c.TId = t.TId
    -> WHERE t.Tname = '张三';
+-----+-------+------------+------+
| Sid | Sname | Sage       | Ssex |
+-----+-------+------------+------+
|   1 | 赵雷  | 1990-01-01 | 男   |
|   2 | 钱电  | 1990-12-21 | 男   |
|   3 | 孙风  | 1990-12-20 | 男   |
|   4 | 李云  | 1990-12-06 | 男   |
|   5 | 周梅  | 1991-12-01 | 女   |
|   7 | 郑竹  | 1989-01-01 | 女   |
+-----+-------+------------+------+
6 rows in set (0.00 sec)

7、查询没有学全所有课程的同学的信息

mysql> select s.* from Student s
    -> join SC sc on
    -> s.Sid = sc.Sid
    -> group by s.Sid
    -> having count(Cid) < 3;
+-----+-------+------------+------+
| Sid | Sname | Sage       | Ssex |
+-----+-------+------------+------+
|   5 | 周梅  | 1991-12-01 | 女   |
|   6 | 吴兰  | 1992-01-01 | 女   |
|   7 | 郑竹  | 1989-01-01 | 女   |
+-----+-------+------------+------+
3 rows in set (0.01 sec)

8、查询至少有一门课与学号为" 01 "的同学所学相同的同学的信息

mysql> select s.* from Student s
    -> join SC sc on
    -> s.Sid = sc.Sid
    -> where sc.Cid in (select Cid from sc where Sid = 1)
    -> and s.Sid != "01";
+-----+-------+------------+------+
| Sid | Sname | Sage       | Ssex |
+-----+-------+------------+------+
|   2 | 钱电  | 1990-12-21 | 男   |
|   3 | 孙风  | 1990-12-20 | 男   |
|   4 | 李云  | 1990-12-06 | 男   |
|   5 | 周梅  | 1991-12-01 | 女   |
|   6 | 吴兰  | 1992-01-01 | 女   |
|   2 | 钱电  | 1990-12-21 | 男   |
|   3 | 孙风  | 1990-12-20 | 男   |
|   4 | 李云  | 1990-12-06 | 男   |
|   5 | 周梅  | 1991-12-01 | 女   |
|   7 | 郑竹  | 1989-01-01 | 女   |
|   2 | 钱电  | 1990-12-21 | 男   |
|   3 | 孙风  | 1990-12-20 | 男   |
|   4 | 李云  | 1990-12-06 | 男   |
|   6 | 吴兰  | 1992-01-01 | 女   |
|   7 | 郑竹  | 1989-01-01 | 女   |
+-----+-------+------------+------+
15 rows in set (0.00 sec)

9、查询和" 01 "号的同学学习的课程完全相同的其他同学的信息

mysql> WITH CourseList01 AS (
    ->     SELECT GROUP_CONCAT(CId ORDER BY CId) AS course_list
    ->     FROM SC
    ->     WHERE SId = '01'
    -> ),
    -> StudentCourses AS (
    ->     SELECT
    ->         SId,
    ->         GROUP_CONCAT(CId ORDER BY CId) AS course_list
    ->     FROM
    ->         SC
    ->     GROUP BY
    ->         SId
    -> )
    -> SELECT
    ->     s.*
    -> FROM
    ->     Student s
    -> JOIN
    ->     StudentCourses sc ON s.SId = sc.SId
    -> JOIN
    ->     CourseList01 cl01 ON sc.course_list = cl01.course_list
    -> WHERE
    ->     s.SId != '01';
+-----+-------+------------+------+
| Sid | Sname | Sage       | Ssex |
+-----+-------+------------+------+
|   2 | 钱电  | 1990-12-21 | 男   |
|   3 | 孙风  | 1990-12-20 | 男   |
|   4 | 李云  | 1990-12-06 | 男   |
+-----+-------+------------+------+
3 rows in set (0.01 sec)

10、查询没学过"张三"老师讲授的任一门课程的学生姓名

mysql> SELECT s.Sname
    -> FROM Student s
    -> WHERE s.SId NOT IN (
    ->     SELECT DISTINCT sc.SId
    ->     FROM SC sc
    ->     JOIN Course c ON sc.CId = c.CId
    ->     JOIN Teacher t ON c.TId = t.TId
    ->     WHERE t.Tname = '张三'
    -> );
+-------+
| Sname |
+-------+
| 吴兰  |
| 张三  |
| 李四  |
| 李四  |
| 赵六  |
| 孙七  |
+-------+
6 rows in set (0.00 sec)

11、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

mysql> SELECT
    ->     s.SId,
    ->     s.Sname,
    ->     AVG(sc.score) AS avg_score
    -> FROM
    ->     Student s
    -> JOIN
    ->     SC sc ON s.SId = sc.SId
    -> WHERE
    ->     s.SId IN (
    ->         SELECT SId
    ->         FROM SC
    ->         WHERE score < 60
    ->         GROUP BY SId
    ->         HAVING COUNT(CId) >= 2
    ->     )
    -> GROUP BY
    ->     s.SId, s.Sname;
+-----+-------+-----------+
| SId | Sname | avg_score |
+-----+-------+-----------+
|   4 | 李云  | 33.333333 |
|   6 | 吴兰  | 32.500000 |
+-----+-------+-----------+
2 rows in set (0.00 sec)

12、检索" 01 "课程分数小于 60，按分数降序排列的学生信息

mysql> select s.*,score from Student s
    -> join SC sc on
    -> s.Sid = sc.Sid
    -> where score < 60 and sc.Cid = "01"
    -> order by score desc;
+-----+-------+------------+------+-------+
| Sid | Sname | Sage       | Ssex | score |
+-----+-------+------------+------+-------+
|   4 | 李云  | 1990-12-06 | 男   | 50.00 |
|   6 | 吴兰  | 1992-01-01 | 女   | 31.00 |
+-----+-------+------------+------+-------+
2 rows in set (0.00 sec)

13、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

mysql> select * from sc
    -> left join (
    ->   select sid,avg(score) as avscore from sc
    ->   group by sid
    ->   )r
    -> on sc.sid = r.sid
    -> order by avscore desc;
+-----+-----+-------+------+-----------+
| SId | CId | score | sid  | avscore   |
+-----+-----+-------+------+-----------+
|   7 |   2 | 89.00 |    7 | 93.500000 |
|   7 |   3 | 98.00 |    7 | 93.500000 |
|   1 |   1 | 80.00 |    1 | 89.666667 |
|   1 |   2 | 90.00 |    1 | 89.666667 |
|   1 |   3 | 99.00 |    1 | 89.666667 |
|   5 |   1 | 76.00 |    5 | 81.500000 |
|   5 |   2 | 87.00 |    5 | 81.500000 |
|   3 |   1 | 80.00 |    3 | 80.000000 |
|   3 |   2 | 80.00 |    3 | 80.000000 |
|   3 |   3 | 80.00 |    3 | 80.000000 |
|   2 |   1 | 70.00 |    2 | 70.000000 |
|   2 |   2 | 60.00 |    2 | 70.000000 |
|   2 |   3 | 80.00 |    2 | 70.000000 |
|   4 |   1 | 50.00 |    4 | 33.333333 |
|   4 |   2 | 30.00 |    4 | 33.333333 |
|   4 |   3 | 20.00 |    4 | 33.333333 |
|   6 |   1 | 31.00 |    6 | 32.500000 |
|   6 |   3 | 34.00 |    6 | 32.500000 |
+-----+-----+-------+------+-----------+

14、查询各科成绩最高分、最低分和平均分：

以如下形式显示：课程 ID，课程 name，最高分，最低分，平均分，及格率，中等率，优良率，优秀率

及格为>=60，中等为：70-80，优良为：80-90，优秀为：>=90

要求输出课程号和选修人数，查询结果按人数降序排列，若人数相同，按课程号升序排列

SELECT 
    c.CId,
    c.Cname,
    COUNT(sc.SId) AS student_count,
    MAX(sc.score) AS max_score,
    MIN(sc.score) AS min_score,
    AVG(sc.score) AS avg_score,
    SUM(CASE WHEN sc.score >= 60 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS pass_rate,
    SUM(CASE WHEN sc.score >= 70 AND sc.score < 80 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS medium_rate,
    SUM(CASE WHEN sc.score >= 80 AND sc.score < 90 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS good_rate,
    SUM(CASE WHEN sc.score >= 90 THEN 1 ELSE 0 END) / COUNT(sc.SId) AS excellent_rate
FROM 
    Course c
JOIN 
    SC sc ON c.CId = sc.CId
GROUP BY 
    c.CId, c.Cname
ORDER BY 
    student_count DESC, c.CId ASC;

15、按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺

select a.cid, a.sid, a.score, count(b.score)+1 as rank
from sc as a 
left join sc as b 
on a.score<b.score and a.cid = b.cid
group by a.cid, a.sid,a.score
order by a.cid, rank ASC;

15.1 、按各科成绩进行排序，并显示排名， Score 重复时合并名次

SELECT 
    CId,
    SId,
    score,
    RANK() OVER (PARTITION BY CId ORDER BY score DESC) AS ranking
FROM 
    SC
ORDER BY 
    CId, ranking;

16、查询学生的总成绩，并进行排名，总分重复时保留名次空缺

mysql> SELECT
    ->     s.SId,
    ->     s.Sname,
    ->     SUM(sc.score) AS total_score,
    ->     DENSE_RANK() OVER (ORDER BY SUM(sc.score) DESC) AS ranking
    -> FROM
    ->     Student s
    -> JOIN
    ->     SC sc ON s.SId = sc.SId
    -> GROUP BY
    ->     s.SId, s.Sname
    -> ORDER BY
    ->     ranking;
+-----+-------+-------------+---------+
| SId | Sname | total_score | ranking |
+-----+-------+-------------+---------+
|   1 | 赵雷  |      269.00 |       1 |
|   3 | 孙风  |      240.00 |       2 |
|   2 | 钱电  |      210.00 |       3 |
|   7 | 郑竹  |      187.00 |       4 |
|   5 | 周梅  |      163.00 |       5 |
|   4 | 李云  |      100.00 |       6 |
|   6 | 吴兰  |       65.00 |       7 |
+-----+-------+-------------+---------+

16.1、查询学生的总成绩，并进行排名，总分重复时不保留名次空缺

SELECT 
    s.SId,
    s.Sname,
    SUM(sc.score) AS total_score,
    ROW_NUMBER() OVER (ORDER BY SUM(sc.score) DESC) AS ranking
FROM 
    Student s
JOIN 
    SC sc ON s.SId = sc.SId
GROUP BY 
    s.SId, s.Sname
ORDER BY 
    ranking;

17、统计各科成绩各分数段人数：课程编号，课程名称，[100-85]，[85-70]，[70-60]，[60-0] 及所占百分比

select course.cname, course.cid,

sum(case when sc.score<=100 and sc.score>85 then 1 else 0 end) as "[100-85]",

sum(case when sc.score<=85 and sc.score>70 then 1 else 0 end) as "[85-70]",

sum(case when sc.score<=70 and sc.score>60 then 1 else 0 end) as "[70-60]",

sum(case when sc.score<=60 and sc.score>0 then 1 else 0 end) as "[60-0]"

from sc left join course

on sc.cid = course.cid

group by sc.cid;

18、查询各科成绩前三名的记录

mysql> select * from sc
    -> where (
    -> select count(*) from sc as a
    -> where sc.cid = a.cid and sc.score<a.score
    -> )< 3
    -> order by cid asc, sc.score desc;
+-----+-----+-------+
| SId | CId | score |
+-----+-----+-------+
|   1 |   1 | 80.00 |
|   3 |   1 | 80.00 |
|   5 |   1 | 76.00 |
|   1 |   2 | 90.00 |
|   7 |   2 | 89.00 |
|   5 |   2 | 87.00 |
|   1 |   3 | 99.00 |
|   7 |   3 | 98.00 |
|   2 |   3 | 80.00 |
|   3 |   3 | 80.00 |
+-----+-----+-------+

19、查询每门课程被选修的学生数

mysql> select cid,count(cid) numbers from sc group by cid;
+-----+---------+
| cid | numbers |
+-----+---------+
|   1 |       6 |
|   2 |       6 |
|   3 |       6 |
+-----+---------+

20、查询出只选修两门课程的学生学号和姓名

mysql> select s.Sid,S.Sname from Student s join
    -> SC sc on
    -> s.Sid = sc.Sid
    -> group by(sid) having count(cid) = 2;
+-----+-------+
| Sid | Sname |
+-----+-------+
|   5 | 周梅  |
|   6 | 吴兰  |
|   7 | 郑竹  |
+-----+-------+
3 rows in set (0.00 sec)

21、查询男生、女生人数

mysql> select Ssex 性别,count(Ssex) 人数
    -> from Student
    -> group by Ssex;
+------+------+
| 性别 | 人数 |
+------+------+
| 男   |    4 |
| 女   |    8 |
+------+------+

22、查询名字中含有「风」字的学生信息

mysql> select * from student
    -> where Sname like "%风%";
+-----+-------+------------+------+
| Sid | Sname | Sage       | Ssex |
+-----+-------+------------+------+
|   3 | 孙风  | 1990-12-20 | 男   |
+-----+-------+------------+------+
1 row in set (0.00 sec)

23、查询同名同性学生名单，并统计同名人数

mysql> select Sname,count(Sname)
    -> from student
    -> group by sname
    -> having count(sname) > 1;
+-------+--------------+
| Sname | count(Sname) |
+-------+--------------+
| 李四  |            2 |
+-------+--------------+
1 row in set (0.00 sec)

24、查询 1990 年出生的学生名单

mysql> select * from
    -> student
    -> where year(Sage) = '1990';
+-----+-------+------------+------+
| Sid | Sname | Sage       | Ssex |
+-----+-------+------------+------+
|   1 | 赵雷  | 1990-01-01 | 男   |
|   2 | 钱电  | 1990-12-21 | 男   |
|   3 | 孙风  | 1990-12-20 | 男   |
|   4 | 李云  | 1990-12-06 | 男   |
+-----+-------+------------+------+
4 rows in set (0.00 sec)

25、查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列

mysql> select Cid 课程号,avg(score) 平均成绩 from
    -> SC
    -> group by Cid
    -> order by avg(score) desc, Cid asc;
+--------+-----------+
| 课程号 | 平均成绩  |
+--------+-----------+
|      2 | 72.666667 |
|      3 | 68.500000 |
|      1 | 64.500000 |
+--------+-----------+
3 rows in set (0.00 sec)

26、查询平均成绩大于等于 85 的所有学生的学号、姓名和平均成绩

mysql> select s.Sid 学号,s.Sname 姓名,avg(sc.score)
    -> from Student s
    -> join SC sc
    -> on s.Sid = sc.Sid
    -> group by s.Sid
    -> having avg(sc.score) >= 85;
+------+------+---------------+
| 学号 | 姓名 | avg(sc.score) |
+------+------+---------------+
|    1 | 赵雷 |     89.666667 |
|    7 | 郑竹 |     93.500000 |
+------+------+---------------+

27、查询课程名称为「数学」，且分数低于 60 的学生姓名和分数

mysql> select s.Sname 姓名,sc.score 数学分数
    -> from Student s
    -> join SC sc
    -> on s.Sid = sc.Sid
    -> where sc.score < 60
    -> and Cid = 2;
+------+----------+
| 姓名 | 数学分数 |
+------+----------+
| 李云 |    30.00 |
+------+----------+

28、查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）

mysql> select s.Sid 学号,s.Sname 姓名,c.Cname 课程,sc.score 分数
    -> from Student s
    -> left join Sc sc on s.Sid = sc.Sid
    -> left join Course c on sc.Cid = c.Cid
    -> ;
+------+------+------+-------+
| 学号 | 姓名 | 课程 | 分数  |
+------+------+------+-------+
|    1 | 赵雷 | 语文 | 80.00 |
|    1 | 赵雷 | 数学 | 90.00 |
|    1 | 赵雷 | 英语 | 99.00 |
|    2 | 钱电 | 语文 | 70.00 |
|    2 | 钱电 | 数学 | 60.00 |
|    2 | 钱电 | 英语 | 80.00 |
|    3 | 孙风 | 语文 | 80.00 |
|    3 | 孙风 | 数学 | 80.00 |
|    3 | 孙风 | 英语 | 80.00 |
|    4 | 李云 | 语文 | 50.00 |
|    4 | 李云 | 数学 | 30.00 |
|    4 | 李云 | 英语 | 20.00 |
|    5 | 周梅 | 语文 | 76.00 |
|    5 | 周梅 | 数学 | 87.00 |
|    6 | 吴兰 | 语文 | 31.00 |
|    6 | 吴兰 | 英语 | 34.00 |
|    7 | 郑竹 | 数学 | 89.00 |
|    7 | 郑竹 | 英语 | 98.00 |
|    9 | 张三 | NULL |  NULL |
|   10 | 李四 | NULL |  NULL |
|   11 | 李四 | NULL |  NULL |
|   12 | 赵六 | NULL |  NULL |
|   13 | 孙七 | NULL |  NULL |
+------+------+------+-------+

29、查询任何一门课程成绩在 70 分以上的姓名、课程名称和分数

mysql> SELECT
    ->     s.Sname,
    ->     c.Cname,
    ->     sc.score
    -> FROM
    ->     Student s
    -> JOIN
    ->     SC sc ON s.SId = sc.SId
    -> JOIN
    ->     Course c ON sc.CId = c.CId
    -> WHERE
    ->     sc.score > 70;
+-------+-------+-------+
| Sname | Cname | score |
+-------+-------+-------+
| 赵雷  | 语文  | 80.00 |
| 孙风  | 语文  | 80.00 |
| 周梅  | 语文  | 76.00 |
| 赵雷  | 数学  | 90.00 |
| 孙风  | 数学  | 80.00 |
| 周梅  | 数学  | 87.00 |
| 郑竹  | 数学  | 89.00 |
| 赵雷  | 英语  | 99.00 |
| 钱电  | 英语  | 80.00 |
| 孙风  | 英语  | 80.00 |
| 郑竹  | 英语  | 98.00 |
+-------+-------+-------+

30、查询不及格的课程

mysql> select Cid 课程号 from SC where score < 60 group by Cid;
+--------+
| 课程号 |
+--------+
|      1 |
|      2 |
|      3 |
+--------+

31、查询课程编号为 01 且课程成绩在 80 分以上的学生的学号和姓名

mysql> select s.Sid 学号,s.Sname from
    -> Student s
    -> join SC sc
    -> where sc.score > 80 and sc.Cid = '01';

32、求每门课程的学生人数

mysql> select Sid 学号,count(Sid) 人数 from sc
    -> group by Sid;
+------+------+
| 学号 | 人数 |
+------+------+
|    1 |    3 |
|    2 |    3 |
|    3 |    3 |
|    4 |    3 |
|    5 |    2 |
|    6 |    2 |
|    7 |    2 |
+------+------+

33、成绩不重复，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩

mysql> SELECT
    ->     student.*,
    ->     sc.score,
    ->     sc.cid
    -> FROM
    ->     student
    -> JOIN
    ->     sc ON student.sid = sc.sid
    -> JOIN
    ->     course ON sc.cid = course.cid
    -> JOIN
    ->     teacher ON course.tid = teacher.tid
    -> WHERE
    ->     teacher.tname = '张三'
    ->     AND sc.score = (
    ->         SELECT MAX(score)
    ->         FROM sc
    ->         JOIN course ON sc.cid = course.cid
    ->         JOIN teacher ON course.tid = teacher.tid
    ->         WHERE teacher.tname = '张三'
    ->     );
+-----+-------+------------+------+-------+-----+
| Sid | Sname | Sage       | Ssex | score | cid |
+-----+-------+------------+------+-------+-----+
|   1 | 赵雷  | 1990-01-01 | 男   | 90.00 |   2 |
+-----+-------+------------+------+-------+-----+
1 row in set (0.00 sec)

34、成绩有重复的情况下，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩

mysql> SELECT
    ->     s.SId,
    ->     s.Sname,
    ->     sc.score
    -> FROM
    ->     Student s
    -> JOIN
    ->     SC sc ON s.SId = sc.SId
    -> JOIN
    ->     Course c ON sc.CId = c.CId
    -> JOIN
    ->     Teacher t ON c.TId = t.TId
    -> WHERE
    ->     t.Tname = '张三'
    ->     AND sc.score = (
    ->         SELECT
    ->             MAX(score)
    ->         FROM
    ->             SC
    ->         JOIN
    ->             Course ON SC.CId = Course.CId
    ->         JOIN
    ->             Teacher ON Course.TId = Teacher.TId
    ->         WHERE
    ->             Teacher.Tname = '张三'
    ->     );
+-----+-------+-------+
| SId | Sname | score |
+-----+-------+-------+
|   1 | 赵雷  | 90.00 |
+-----+-------+-------+

35、查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩

mysql> SELECT
    ->     sc1.SId,
    ->     sc1.CId AS course_id_1,
    ->     sc2.CId AS course_id_2,
    ->     sc1.score
    -> FROM
    ->     SC sc1
    -> JOIN
    ->     SC sc2
    -> ON
    ->     sc1.SId = sc2.SId
    ->     AND sc1.CId < sc2.CId
    ->     AND sc1.score = sc2.score;
+-----+-------------+-------------+-------+
| SId | course_id_1 | course_id_2 | score |
+-----+-------------+-------------+-------+
|   3 |           1 |           2 | 80.00 |
|   3 |           1 |           3 | 80.00 |
|   3 |           2 |           3 | 80.00 |
+-----+-------------+-------------+-------+
3 rows in set (0.00 sec)

36、查询每门功成绩最好的前两名

mysql> select a.sid,a.cid,a.score from sc as a
    -> left join sc as b
    -> on a.cid = b.cid and a.score<b.score
    -> group by a.cid, a.sid
    -> having count(b.cid)<2
    -> order by a.cid;
+-----+-----+-------+
| sid | cid | score |
+-----+-----+-------+
|   1 |   1 | 80.00 |
|   3 |   1 | 80.00 |
|   1 |   2 | 90.00 |
|   7 |   2 | 89.00 |
|   1 |   3 | 99.00 |
|   7 |   3 | 98.00 |
+-----+-----+-------+

37、统计每门课程的学生选修人数（超过 5 人的课程才统计）。

mysql> SELECT
    ->     CId,
    ->     COUNT(SId) AS enrollment_count
    -> FROM
    ->     SC
    -> GROUP BY
    ->     CId
    -> HAVING
    ->     COUNT(SId) > 5
    -> ORDER BY
    ->     CId;
+-----+------------------+
| CId | enrollment_count |
+-----+------------------+
|   1 |                6 |
|   2 |                6 |
|   3 |                6 |
+-----+------------------+

38、检索至少选修两门课程的学生学号

mysql> select Sid 学号,count(Cid) 选修课程数
    -> from sc
    -> group by Sid
    -> having count(Cid) >= 2;
+------+------------+
| 学号 | 选修课程数 |
+------+------------+
|    1 |          3 |
|    2 |          3 |
|    3 |          3 |
|    4 |          3 |
|    5 |          2 |
|    6 |          2 |
|    7 |          2 |
+------+------------+

39、查询选修了全部课程的学生信息

mysql> select student.*
    -> from sc ,student
    -> where sc.SId=student.SId
    -> GROUP BY sc.SId
    -> HAVING count(*) = (select DISTINCT count(*) from course )
    -> ;
+-----+-------+------------+------+
| Sid | Sname | Sage       | Ssex |
+-----+-------+------------+------+
|   1 | 赵雷  | 1990-01-01 | 男   |
|   2 | 钱电  | 1990-12-21 | 男   |
|   3 | 孙风  | 1990-12-20 | 男   |
|   4 | 李云  | 1990-12-06 | 男   |
+-----+-------+------------+------+

40、查询各学生的年龄，只按年份来算

mysql> SELECT
    ->     SId,
    ->     Sname,
    ->     YEAR(CURDATE()) - YEAR(Sage) AS age
    -> FROM
    ->     Student;
+-----+-------+------+
| SId | Sname | age  |
+-----+-------+------+
|   1 | 赵雷  |   35 |
|   2 | 钱电  |   35 |
|   3 | 孙风  |   35 |
|   4 | 李云  |   35 |
|   5 | 周梅  |   34 |
|   6 | 吴兰  |   33 |
|   7 | 郑竹  |   36 |
|   9 | 张三  |    8 |
|  10 | 李四  |    8 |
|  11 | 李四  |   13 |
|  12 | 赵六  |   12 |
|  13 | 孙七  |   11 |
+-----+-------+------+

42、查询本周过生日的学生

mysql> select *
    ->
    -> from student
    ->
    -> where WEEKOFYEAR(student.Sage)=WEEKOFYEAR(CURDATE());
Empty set (0.00 sec)

43、查询下周过生日的学生

mysql> select *
    ->
    -> from student
    ->
    -> where WEEKOFYEAR(student.Sage)=WEEKOFYEAR(CURDATE())+1;
Empty set (0.00 sec)

44、查询本月过生日的学生

mysql> select * from student  
  -> where MONTH(student.Sage) = MONTH(CURDATE());
    Empty set (0.00 sec)

45、查询下月过生日的学生

mysql> select * from student
    -> where MONTH(student.Sage) = MONTH(CURDATE()) + 1;
Empty set (0.00 sec)

MySQL作业三（MySQL练习50题）

学生成绩

1、创建表

1）学生表

2）课程表

3）教师表

4）成绩表

2、插入数据

1）学生Student

2）科目表Course

3）教师表 Teacher

4）成绩表 SC

3、练习题目

1、查询" 01 "课程比" 02 "课程成绩高的学生的信息及课程分数、

1.1、 查询同时存在" 01 "课程和" 02 "课程的情况

1.2、 查询存在" 01 "课程但可能不存在" 02 "课程的情况(不存在时显示为 null )

1.3 、查询不存在" 01 "课程但存在" 02 "课程的情况

2、查询平均成绩大于等于 60 分的同学的学生编号和学生姓名和平均成绩

3、查询在 SC 表存在成绩的学生信息

4、查询所有同学的学生编号、学生姓名、选课总数、所有课程的总成绩(没成绩的显示为 null )

4.1 、查有成绩的学生信息

5、查询「李」姓老师的数量

6、查询学过「张三」老师授课的同学的信息

7、查询没有学全所有课程的同学的信息

8、查询至少有一门课与学号为" 01 "的同学所学相同的同学的信息

9、查询和" 01 "号的同学学习的课程 完全相同的其他同学的信息

10、查询没学过"张三"老师讲授的任一门课程的学生姓名

11、查询两门及其以上不及格课程的同学的学号，姓名及其平均成绩

12、检索" 01 "课程分数小于 60，按分数降序排列的学生信息

13、按平均成绩从高到低显示所有学生的所有课程的成绩以及平均成绩

14、查询各科成绩最高分、最低分和平均分：

15、按各科成绩进行排序，并显示排名， Score 重复时保留名次空缺

15.1 、按各科成绩进行排序，并显示排名， Score 重复时合并名次

16、查询学生的总成绩，并进行排名，总分重复时保留名次空缺

16.1、查询学生的总成绩，并进行排名，总分重复时不保留名次空缺

17、统计各科成绩各分数段人数：课程编号，课程名称，[100-85]，[85-70]，[70-60]，[60-0] 及所占百分比

18、查询各科成绩前三名的记录

19、查询每门课程被选修的学生数

20、查询出只选修两门课程的学生学号和姓名

21、查询男生、女生人数

22、查询名字中含有「风」字的学生信息

23、查询同名同性学生名单，并统计同名人数

24、查询 1990 年出生的学生名单

25、查询每门课程的平均成绩，结果按平均成绩降序排列，平均成绩相同时，按课程编号升序排列

26、查询平均成绩大于等于 85 的所有学生的学号、姓名和平均成绩

27、查询课程名称为「数学」，且分数低于 60 的学生姓名和分数

28、查询所有学生的课程及分数情况（存在学生没成绩，没选课的情况）

29、查询任何一门课程成绩在 70 分以上的姓名、课程名称和分数

30、查询不及格的课程

31、查询课程编号为 01 且课程成绩在 80 分以上的学生的学号和姓名

32、求每门课程的学生人数

33、成绩不重复，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩

34、成绩有重复的情况下，查询选修「张三」老师所授课程的学生中，成绩最高的学生信息及其成绩

35、查询不同课程成绩相同的学生的学生编号、课程编号、学生成绩

36、查询每门功成绩最好的前两名

37、统计每门课程的学生选修人数（超过 5 人的课程才统计）。

38、检索至少选修两门课程的学生学号

39、查询选修了全部课程的学生信息

40、查询各学生的年龄，只按年份来算

42、查询本周过生日的学生

43、查询下周过生日的学生

44、查询本月过生日的学生

45、查询下月过生日的学生

1.1、查询同时存在" 01 "课程和" 02 "课程的情况

1.2、查询存在" 01 "课程但可能不存在" 02 "课程的情况(不存在时显示为 null )

9、查询和" 01 "号的同学学习的课程完全相同的其他同学的信息