一些简单的mysql综合练习

墨蓝 2021-09-24 14:54 300阅读 0赞

下面做一系列mysql的综合练习

新建一个查询用的数据库:selectTest

CREATE DATABASE selectTest;

选择该数据库:

USE selectTest;

创建学生表:student  
学号  
姓名  
性别  
出生日期  
所在班级

CREATE TABLE student(
        s_no VARCHAR(20) PRIMARY KEY COMMENT'学生学号',
        s_name VARCHAR(20) NOT NULL COMMENT'学生姓名 不能为空',
        s_sex VARCHAR(10) NOT NULL COMMENT'学生性别',
        s_birthday DATETIME COMMENT'学生生日',
        s_class VARCHAR(20) COMMENT'学生所在的班级'
    );

创建课程表:  
course  
课程号  
课程课程名称  
教师编号

CREATE TABLE course(
        c_no VARCHAR(20) PRIMARY KEY COMMENT'课程号',
        c_name VARCHAR(20) NOT NULL COMMENT'课程名称',
        t_no VARCHAR(20) NOT NULL COMMENT'教师编号 外键关联teacher表',
        FOREIGN KEY(t_no) references teacher(t_no)
    );

ps：要先创建教师表

教师表  
teacher  
教师编号  
教师名字  
教师性别  
出生日期  
职称  
所在部门

CREATE TABLE teacher(
        t_no VARCHAR(20) PRIMARY KEY COMMENT'教师编号',
        t_name VARCHAR(20) NOT NULL COMMENT'教师姓名',
        t_sex VARCHAR(20) NOT NULL COMMENT'教师性别',
        t_birthday DATETIME COMMENT'教师生日',
        t_rof VARCHAR(20) NOT NULL COMMENT'教师职称',
        t_depart VARCHAR(20) NOT NULL COMMENT'教师所在的部门'
    );

成绩表srore  
学号  
课程号  
成绩  
注意:视频中原先只有一个主键s\_no ,后来修改了

CREATE TABLE score (
        s_no VARCHAR(20) NOT NULL COMMENT'成绩表的编号 依赖学生学号',
            c_no VARCHAR(20)  NOT NULL COMMENT'课程号 依赖于课程表中的c_id',
        sc_degree decimal,
        foreign key(s_no) references student(s_no),
        foreign key(c_no) references course(c_no),
        PRIMARY KEY(s_no,c_no)
    );

查看创建的表以及架构

查看student表结构

查看teacher表结构

查看course表结构

DESCRIBE course;
    +--------+-------------+------+-----+---------+-------+
    | Field  | Type        | Null | Key | Default | Extra |
    +--------+-------------+------+-----+---------+-------+
    | c_no   | varchar(20) | NO   | PRI | NULL    |       |
    | c_name | varchar(20) | NO   |     | NULL    |       |
    | t_no   | varchar(20) | NO   | MUL | NULL    |       |
    +--------+-------------+------+-----+---------+-------+

查看score表结构

DESCRIBE score;
    +-----------+---------------+------+-----+---------+-------+
    | Field     | Type          | Null | Key | Default | Extra |
    +-----------+---------------+------+-----+---------+-------+
    | s_no      | varchar(20)   | NO   | PRI | NULL    |       |
    | c_no      | varchar(20)   | NO   | MUL | NULL    |       |
    | sc_degree | decimal(10,0) | YES  |     | NULL    |       |
    +-----------+---------------+------+-----+---------+-------+

向表中添加数据

–学生表数据

INSERT INTO student VALUES('101','曾华','男','1977-09-01','95033');
    INSERT INTO student VALUES('102','匡明','男','1975-10-02','95031');
    INSERT INTO student VALUES('103','王丽','女','1976-01-23','95033');
    INSERT INTO student VALUES('104','李军','男','1976-02-20','95033');
    INSERT INTO student VALUES('105','王芳','女','1975-02-10','95031');
    INSERT INTO student VALUES('106','陆军','男','1974-06-03','95031');
    INSERT INTO student VALUES('107','王尼玛','男','1976-02-20','95033');
    INSERT INTO student VALUES('108','张全蛋','男','1975-02-10','95031');
    INSERT INTO student VALUES('109','赵铁柱','男','1974-06-03','95031');

–教师表数据

INSERT INTO teacher VALUES('804','李诚','男','1958-12-02','副教授','计算机系');
    INSERT INTO teacher VALUES('856','张旭','男','1969-03-12','讲师','电子工程系');
    INSERT INTO teacher VALUES('825','王萍','女','1972-05-05','助教','计算机系');
    INSERT INTO teacher VALUES('831','刘冰','女','1977-08-14','助教','电子工程系');

–添加课程表

INSERT INTO course VALUES('3-105','计算机导论','825');
    INSERT INTO course VALUES('3-245','操作系统','804');
    INSERT INTO course VALUES('6-166','数字电路','856');
    INSERT INTO course VALUES('9-888','高等数学','831');

–添加成绩表

INSERT INTO score VALUES('103','3-245','86');
    INSERT INTO score VALUES('105','3-245','75');
    INSERT INTO score VALUES('109','3-245','68');
    INSERT INTO score VALUES('103','3-105','92');
    
    INSERT INTO score VALUES('105','3-105','88');
    INSERT INTO score VALUES('109','3-105','76');
    INSERT INTO score VALUES('103','6-166','85');
    
    INSERT INTO score VALUES('105','6-166','79');
    INSERT INTO score VALUES('109','6-166','81');

几张表的数据展现

student   SELECT * FROM student;
    +------+--------+-------+---------------------+---------+
    | s_no | s_name | s_sex | s_birthday          | s_class |
    +------+--------+-------+---------------------+---------+
    | 101  | 曾华   | 男    | 1977-09-01 00:00:00 | 95033   |
    | 102  | 匡明   | 男    | 1975-10-02 00:00:00 | 95031   |
    | 103  | 王丽   | 女    | 1976-01-23 00:00:00 | 95033   |
    | 104  | 李军   | 男    | 1976-02-20 00:00:00 | 95033   |
    | 105  | 王芳   | 女    | 1975-02-10 00:00:00 | 95031   |
    | 106  | 陆军   | 男    | 1974-06-03 00:00:00 | 95031   |
    | 107  | 王尼玛 | 男    | 1976-02-20 00:00:00 | 95033   |
    | 108  | 张全蛋 | 男    | 1975-02-10 00:00:00 | 95031   |
    | 109  | 赵铁柱 | 男    | 1974-06-03 00:00:00 | 95031   |
    +------+--------+-------+---------------------+---------+
    
    teacher  SELECT * FROM teacher;
    +------+--------+-------+---------------------+--------+------------+
    | t_no | t_name | t_sex | t_birthday          | t_rof  | t_depart   |
    +------+--------+-------+---------------------+--------+------------+
    | 804  | 李诚   | 男    | 1958-12-02 00:00:00 | 副教授 | 计算机系   |
    | 825  | 王萍   | 女    | 1972-05-05 00:00:00 | 助教   | 计算机机系 |
    | 831  | 刘冰   | 女    | 1977-08-14 00:00:00 | 助教   | 电子工程系 |
    | 856  | 张旭   | 男    | 1969-03-12 00:00:00 | 讲师   | 电子工程系 |
    +------+--------+-------+---------------------+--------+------------+
    
    score  SELECT * FROM score;
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 103  | 3-105 |        92 |
    | 103  | 3-245 |        86 |
    | 103  | 6-166 |        85 |
    | 105  | 3-105 |        88 |
    | 105  | 3-245 |        75 |
    | 105  | 6-166 |        79 |
    | 109  | 3-105 |        76 |
    | 109  | 3-245 |        68 |
    | 109  | 6-166 |        81 |
    +------+-------+-----------+
    
    course    SELECT * FROM course;
    +-------+------------+------+
    | c_no  | c_name     | t_no |
    +-------+------------+------+
    | 3-105 | 计算机导论 | 825  |
    | 3-245 | 操作系统   | 804  |
    | 6-166 | 数字电路   | 856  |
    | 9-888 | 高等数学   | 831  |
    +-------+------------+------+

查询联系  
– 1.查询student表中所有的记录

SELECT * FROM student;
    +------+--------+-------+---------------------+---------+
    | s_no | s_name | s_sex | s_birthday          | s_class |
    +------+--------+-------+---------------------+---------+
    | 1    | admin  | 男    | 1999-09-09 00:00:00 | 95033   |
    | 101  | 曾华   | 男    | 1977-09-01 00:00:00 | 95033   |
    | 102  | 匡明   | 男    | 1975-10-02 00:00:00 | 95031   |
    | 103  | 王丽   | 女    | 1976-01-23 00:00:00 | 95033   |
    | 104  | 李军   | 男    | 1976-02-20 00:00:00 | 95033   |
    | 105  | 王芳   | 女    | 1975-02-10 00:00:00 | 95031   |
    | 106  | 陆军   | 男    | 1974-06-03 00:00:00 | 95031   |
    | 107  | 王尼玛 | 男    | 1976-02-20 00:00:00 | 95033   |
    | 108  | 张全蛋 | 男    | 1975-02-10 00:00:00 | 95031   |
    | 109  | 赵铁柱 | 男    | 1974-06-03 00:00:00 | 95031   |
    +------+--------+-------+---------------------+---------+

– 2.查询student表中所有记录的s\_name,s\_sex和s\_class列

SELECT s_no,s_name,s_class FROM  student;
    +------+--------+---------+
    | s_no | s_name | s_class |
    +------+--------+---------+
    | 1    | admin  | 95033   |
    | 101  | 曾华   | 95033   |
    | 102  | 匡明   | 95031   |
    | 103  | 王丽   | 95033   |
    | 104  | 李军   | 95033   |
    | 105  | 王芳   | 95031   |
    | 106  | 陆军   | 95031   |
    | 107  | 王尼玛 | 95033   |
    | 108  | 张全蛋 | 95031   |
    | 109  | 赵铁柱 | 95031   |
    +------+--------+---------+

– 3.查询教师所有的单位但是不重复的t\_depart列

– 4.查询score表中成绩在60-80之间所有的记录(sc\_degree)  
注意:BETWEEN… ADN… 是包含边界的

SELECT * FROM score WHERE sc_degree BETWEEN 61 AND 79;
    SELECT * FROM score WHERE sc_degree < 80 AND sc_degree > 60 ; 
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 105  | 3-245 |        75 |
    | 105  | 6-166 |        79 |
    | 109  | 3-105 |        76 |
    | 109  | 3-245 |        68 |
    +------+-------+-----------+

– 5.查询score表中成绩为85, 86, 或者88的记录(sc\_degree)

SELECT * FROM score WHERE sc_degree IN(85, 86, 88);
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 103  | 3-245 |        86 |
    | 103  | 6-166 |        85 |
    | 105  | 3-105 |        88 |
    +------+-------+-----------+

– 6.查询student表中’95031’班或者性别为’女’的同学记录

SELECT * FROM student WHERE s_class = '95031' OR s_sex = '女';
    +------+--------+-------+---------------------+---------+
    | s_no | s_name | s_sex | s_birthday          | s_class |
    +------+--------+-------+---------------------+---------+
    | 102  | 匡明   | 男    | 1975-10-02 00:00:00 | 95031   |
    | 103  | 王丽   | 女    | 1976-01-23 00:00:00 | 95033   |
    | 105  | 王芳   | 女    | 1975-02-10 00:00:00 | 95031   |
    | 106  | 陆军   | 男    | 1974-06-03 00:00:00 | 95031   |
    | 108  | 张全蛋 | 男    | 1975-02-10 00:00:00 | 95031   |
    | 109  | 赵铁柱 | 男    | 1974-06-03 00:00:00 | 95031   |
    +------+--------+-------+---------------------+---------+

– 7.以class降序查询student表中所有的记录

SELECT * FROM student ORDER BY s_class desc;
    +------+--------+-------+---------------------+---------+
    | s_no | s_name | s_sex | s_birthday          | s_class |
    +------+--------+-------+---------------------+---------+
    | 1    | admin  | 男    | 1999-09-09 00:00:00 | 95033   |
    | 101  | 曾华   | 男    | 1977-09-01 00:00:00 | 95033   |
    | 103  | 王丽   | 女    | 1976-01-23 00:00:00 | 95033   |
    | 104  | 李军   | 男    | 1976-02-20 00:00:00 | 95033   |
    | 107  | 王尼玛 | 男    | 1976-02-20 00:00:00 | 95033   |
    | 102  | 匡明   | 男    | 1975-10-02 00:00:00 | 95031   |
    | 105  | 王芳   | 女    | 1975-02-10 00:00:00 | 95031   |
    | 106  | 陆军   | 男    | 1974-06-03 00:00:00 | 95031   |
    | 108  | 张全蛋 | 男    | 1975-02-10 00:00:00 | 95031   |
    | 109  | 赵铁柱 | 男    | 1974-06-03 00:00:00 | 95031   |
    +------+--------+-------+---------------------+---------+

– 8.以c\_no升序.sc\_degree降序插叙score表中所有的数据  
先以c\_no进行升序,若c\_no相同,则以sc\_degree降序

SELECT * FROM score ORDER BY c_no ASC,sc_degree DESC;
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 103  | 3-105 |        92 |
    | 105  | 3-105 |        88 |
    | 109  | 3-105 |        76 |
    | 103  | 3-245 |        86 |
    | 105  | 3-245 |        75 |
    | 109  | 3-245 |        68 |
    | 103  | 6-166 |        85 |
    | 109  | 6-166 |        81 |
    | 105  | 6-166 |        79 |
    +------+-------+-----------+

– 9.查询’95031’班的学生人数

SELECT COUNT(s_no) FROM student WHERE s_class = '95031';
    +-------------+
    | COUNT(s_no) |
    +-------------+
    |           5 |
    +-------------+

– 10.查询score表中的最高分数的学生号和课程号.(子查询或者排序)  
–查询步骤  
1.先找到最高分  
最高分: SELECT MAX(sc\_degree) FROM score;  
2.通过我们找到的最高分的分数来从score中找到我们需要的学生号和课程号

SELECT c_no, s_no FROM score WHERE sc_degree = (最高分)
    
    SELECT c_no, s_no FROM score WHERE sc_degree = (SELECT MAX(sc_degree) FROM score);
    +-------+------+
    | c_no  | s_no |
    +-------+------+
    | 3-105 | 103  |
    +-------+------+
    
    排序 最高分有多个的情况下可能有数据问题
    limit x,y  (x:表示从X条数据开始  y:需要查出多少条)
    SELECT c_no, s_no FROM score ORDER BY sc_degree DESC LIMIT 0,1;这个OK
    但是我们再插入一条数据:
    INSERT INTO score VALUES('101','9-888','92');
    再用排序法去查得到:
    +-------+------+
    | c_no  | s_no |
    +-------+------+
    | 9-888 | 101  |
    +-------+------+
    有两条数据但是只显示一条,有问题
    
    若我们用子查询的方法来查询的话会得到:
    +-------+------+
    | c_no  | s_no |
    +-------+------+
    | 9-888 | 101  |
    | 3-105 | 103  |
    +-------+------+
    完全没有问题.
    最后为了和视频数据一致删除刚刚插入的数据:
    DELETE FROM score WHERE c_no = '9-888' AND s_no = '101';

– 11.查询每门课的平均成绩

SELECT c_no,AVG(sc_degree) FROM SCORE GROUP BY c_no;
    +-------+----------------+
    | c_no  | AVG(sc_degree) |
    +-------+----------------+
    | 3-105 |        87.6667 |
    | 3-245 |        76.3333 |
    | 6-166 |        81.6667 |
    +-------+----------------+

– 12,查询score表中至少有2名学生选修的,并且以3开头的课程的平均分

SELECT AVG(sc_degree),c_no  from score GROUP BY c_no HAVING COUNT(c_no)  >= 2 AND c_no like '3%'  ;
    +----------------+-------+
    | AVG(sc_degree) | c_no  |
    +----------------+-------+
    |        85.3333 | 3-105 |
    |        76.3333 | 3-245 |
    +----------------+-------+

– 13.查询分数大于70但是小于90的s\_no列:

SELECT s_no,sc_degree  FROM score WHERE sc_degree BETWEEN 71 AND 89;
    +------+-----------+
    | s_no | sc_degree |
    +------+-----------+
    | 103  |        86 |
    | 103  |        85 |
    | 105  |        88 |
    | 105  |        75 |
    | 105  |        79 |
    | 109  |        76 |
    | 109  |        81 |
    +------+-----------+

进阶:显示s\_name,c\_name

select s_name,sc_degree,c_name FROM score,student,course WHERE score.s_no = student.s_no AND score.c_no = course.c_no AND sc_degree BETWEEN 71 AND 89;
    +--------+-----------+------------+
    | s_name | sc_degree | c_name     |
    +--------+-----------+------------+
    | 王丽   |        86 | 操作系统   |
    | 王丽   |        85 | 数字电路   |
    | 王芳   |        88 | 计算机导论 |
    | 王芳   |        75 | 操作系统   |
    | 王芳   |        79 | 数字电路   |
    | 赵铁柱 |        76 | 计算机导论 |
    | 赵铁柱 |        81 | 数字电路   |
    +--------+-----------+------------+

– 14.查询所有的学生 s\_name , c\_no, sc\_degree列

SELECT s_name, c_no, sc_degree FROM student,score WHERE student.s_no = score.s_no;
    +--------+-------+-----------+
    | s_name | c_no  | sc_degree |
    +--------+-------+-----------+
    | 王丽   | 3-105 |        92 |
    | 王丽   | 3-245 |        86 |
    | 王丽   | 6-166 |        85 |
    | 王芳   | 3-105 |        88 |
    | 王芳   | 3-245 |        75 |
    | 王芳   | 6-166 |        79 |
    | 赵铁柱 | 3-105 |        76 |
    | 赵铁柱 | 3-245 |        68 |
    | 赵铁柱 | 6-166 |        81 |
    +--------+-------+-----------+

– 15.查询所有学生的s\_no, c\_name, sc\_degree列

SELECT student.s_no, c_name, sc_degree FROM student, course,score WHERE student.s_no = score.s_no AND score.c_no = course.c_no ;
    +------+------------+-----------+
    | s_no | c_name     | sc_degree |
    +------+------------+-----------+
    | 103  | 计算机导论 |        92 |
    | 103  | 操作系统   |        86 |
    | 103  | 数字电路   |        85 |
    | 105  | 计算机导论 |        88 |
    | 105  | 操作系统   |        75 |
    | 105  | 数字电路   |        79 |
    | 109  | 计算机导论 |        76 |
    | 109  | 操作系统   |        68 |
    | 109  | 数字电路   |        81 |
    +------+------------+-----------+

– 16.查询所有的学生 s\_name , c\_name, sc\_degree列  
将上面的c\_no 的值换位c\_name

SELECT s_name, c_name, sc_degree FROM student, course, score WHERE student.s_no = score.s_no AND score.c_no = course.c_no;
    +--------+------------+-----------+
    | s_name | c_name     | sc_degree |
    +--------+------------+-----------+
    | 王丽   | 计算机导论 |        92 |
    | 王丽   | 操作系统   |        86 |
    | 王丽   | 数字电路   |        85 |
    | 王芳   | 计算机导论 |        88 |
    | 王芳   | 操作系统   |        75 |
    | 王芳   | 数字电路   |        79 |
    | 赵铁柱 | 计算机导论 |        76 |
    | 赵铁柱 | 操作系统   |        68 |
    | 赵铁柱 | 数字电路   |        81 |
    +--------+------------+-----------+

– 17.查询班级是’95031’班学生每门课的平均分

select c_no,AVG(sc_degree) from score WHERE s_no IN (select s_no from student where s_class = '95031') GROUP BY c_no;
    
    select c_no,AVG(sc_degree) from score AS sc LEFT JOIN student AS s ON sc.s_no = s.s_no WHERE s.s_class = '95031' GROUP BY sc.c_no;
    
    SELECT sc.c_no,AVG(sc.sc_degree) FROM student AS s, score AS SC  WHERE s.s_class = '95031' AND s.s_no = sc.s_no GROUP BY sc.c_no ;
    +-------+-------------------+
    | c_no  | AVG(sc.sc_degree) |
    +-------+-------------------+
    | 3-105 |           82.0000 |
    | 3-245 |           71.5000 |
    | 6-166 |           80.0000 |
    +-------+-------------------+
    进阶,加入课程名称:
    SELECT sc.c_no, c.c_name, AVG(sc.sc_degree) FROM student AS s, score AS SC, course AS c  WHERE s.s_class = '95031' AND s.s_no = sc.s_no AND c.c_no = sc.c_no GROUP BY sc.c_no ;
    +-------+------------+-------------------+
    | c_no  | c_name     | AVG(sc.sc_degree) |
    +-------+------------+-------------------+
    | 3-105 | 计算机导论 |           82.0000 |
    | 3-245 | 操作系统   |           71.5000 |
    | 6-166 | 数字电路   |           80.0000 |
    +-------+------------+-------------------+

– 18.查询选修"3-105"课程的成绩高于’109’号同学’3-105’成绩 的所有同学的记录

(在大家都在选修3-105的背景下 查询 所有 分数 比 学号为"109"还要高的学生信息)
    SELECT * FROM student AS s, score AS sc WHERE sc.c_no = '3-105' AND sc.sc_degree > (SELECT sc_degree FROM score WHERE s_no = '109' AND c_no = '3-105') AND s.s_no = sc.s_no;
    
    
    +------+--------+-------+---------------------+---------+------+-------+-----------+
    | s_no | s_name | s_sex | s_birthday          | s_class | s_no | c_no  | sc_degree |
    +------+--------+-------+---------------------+---------+------+-------+-----------+
    | 103  | 王丽   | 女    | 1976-01-23 00:00:00 | 95033   | 103  | 3-105 |        92 |
    | 105  | 王芳   | 女    | 1975-02-10 00:00:00 | 95031   | 105  | 3-105 |        88 |
    +------+--------+-------+---------------------+---------+------+-------+-----------+

– 19.查询成绩高于学号为’109’,课程号为’3-105’的成绩的所有记录

SELECT * FROM score WHERE sc_degree >(SELECT sc_degree FROM score WHERE s_no = '109' AND c_no = '3-105');
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 103  | 3-105 |        92 |
    | 103  | 3-245 |        86 |
    | 103  | 6-166 |        85 |
    | 105  | 3-105 |        88 |
    | 105  | 6-166 |        79 |
    | 109  | 6-166 |        81 |
    +------+-------+-----------+
    
    查出来了score记录,但是并没有学生的信息,按照上面的来修改:
    SELECT * FROM student AS s, score AS sc WHERE sc.sc_degree > (SELECT sc_degree FROM score WHERE s_no = '109' AND c_no = '3-105') AND s.s_no = sc.s_no;
    
    还可以再进一步:
    SELECT s.s_no AS'学生学号', s.s_name AS'学生姓名', s_sex AS'性别', s_class AS'班级', c.c_no AS'课程编号', c.c_name AS'课程名称' ,sc.sc_degree AS'分数' FROM student AS s, score AS sc ,course AS c WHERE sc.sc_degree > (SELECT sc_degree FROM score WHERE s_no = '109' AND c_no = '3-105') AND s.s_no = sc.s_no AND sc.c_no = c.c_no;
    +----------+----------+------+-------+----------+------------+------+
    | 学生学号 | 学生姓名 | 性别 | 班级  | 课程编号 | 课程名称   | 分数 |
    +----------+----------+------+-------+----------+------------+------+
    | 103      | 王丽     | 女   | 95033 | 3-105    | 计算机导论 |   92 |
    | 103      | 王丽     | 女   | 95033 | 3-245    | 操作系统   |   86 |
    | 103      | 王丽     | 女   | 95033 | 6-166    | 数字电路   |   85 |
    | 105      | 王芳     | 女   | 95031 | 3-105    | 计算机导论 |   88 |
    | 105      | 王芳     | 女   | 95031 | 6-166    | 数字电路   |   79 |
    | 109      | 赵铁柱   | 男   | 95031 | 6-166    | 数字电路   |   81 |
    +----------+----------+------+-------+----------+------------+------+

– 20.查询所有学号为108.101的同学同年出生的所有学生的s\_no,s\_name和s\_birthday

SELECT * FROM student WHERE YEAR(s_birthday) IN (SELECT YEAR(s_birthday) FROM student WHERE s_no IN('108','101'));
    +------+--------+-------+---------------------+---------+
    | s_no | s_name | s_sex | s_birthday          | s_class |
    +------+--------+-------+---------------------+---------+
    | 101  | 曾华   | 男    | 1977-09-01 00:00:00 | 95033   |
    | 102  | 匡明   | 男    | 1975-10-02 00:00:00 | 95031   |
    | 105  | 王芳   | 女    | 1975-02-10 00:00:00 | 95031   |
    | 108  | 张全蛋 | 男    | 1975-02-10 00:00:00 | 95031   |
    +------+--------+-------+---------------------+---------+

– 21.查询 张旭 教师任课的学生的成绩

select * from student where s_no IN (SELECT s_no FROM score WHERE c_no = (SELECT c_no FROM course WHERE t_no = (SELECT t_no FROM teacher WHERE t_name='张旭')));
    
    +------+--------+-------+---------------------+---------+
    | s_no | s_name | s_sex | s_birthday          | s_class |
    +------+--------+-------+---------------------+---------+
    | 103  | 王丽   | 女    | 1976-01-23 00:00:00 | 95033   |
    | 105  | 王芳   | 女    | 1975-02-10 00:00:00 | 95031   |
    | 109  | 赵铁柱 | 男    | 1974-06-03 00:00:00 | 95031   |
    +------+--------+-------+---------------------+---------+

– 22.查询选修课程的同学人数多余 5 人的教师姓名

SELECT * FROM teacher WHERE t_no IN(SELECT t_no FROM course WHERE c_no IN (SELECT c_no FROM score GROUP BY c_no HAVING COUNT(s_no) > 5));
    
    Empty set (0.00 sec)      没有符合条件的
    为了效果,添加数据:
    INSERT INTO score VALUES('101','3-105','90');
    INSERT INTO score VALUES('102','3-105','91');
    INSERT INTO score VALUES('104','3-105','89');
    
    再次查询可得:
    +------+--------+-------+---------------------+-------+------------+
    | t_no | t_name | t_sex | t_birthday          | t_rof | t_depart   |
    +------+--------+-------+---------------------+-------+------------+
    | 825  | 王萍   | 女    | 1972-05-05 00:00:00 | 助教  | 计算机机系 |
    +------+--------+-------+---------------------+-------+------------+
    注意:视频中用 '=' 是不严谨的,实际中你根本不知道有多少条件是符合的,要用IN

– 23.查询95033班和95031班全体学生的记录

SELECT * FROM student WHERE s_class IN('95031','95033') ORDER BY s_class ;
    +------+--------+-------+---------------------+---------+
    | s_no | s_name | s_sex | s_birthday          | s_class |
    +------+--------+-------+---------------------+---------+
    | 102  | 匡明   | 男    | 1975-10-02 00:00:00 | 95031   |
    | 105  | 王芳   | 女    | 1975-02-10 00:00:00 | 95031   |
    | 106  | 陆军   | 男    | 1974-06-03 00:00:00 | 95031   |
    | 108  | 张全蛋 | 男    | 1975-02-10 00:00:00 | 95031   |
    | 109  | 赵铁柱 | 男    | 1974-06-03 00:00:00 | 95031   |
    | 101  | 曾华   | 男    | 1977-09-01 00:00:00 | 95033   |
    | 103  | 王丽   | 女    | 1976-01-23 00:00:00 | 95033   |
    | 104  | 李军   | 男    | 1976-02-20 00:00:00 | 95033   |
    | 107  | 王尼玛 | 男    | 1976-02-20 00:00:00 | 95033   |
    +------+--------+-------+---------------------+---------+
    
    由于只有这两个班,所以要插入数据:
    INSERT INTO student VALUES('110','张飞','男','1974-06-03','95038');
    再次查询,还是上面那些
    
    我在写的时候,写成了:查询95033班和95031班全体学生每门课的成绩以及负责该课程的老师,最后以class来排序
    写都写了,那就放出来:
    SELECT s.s_no, s.s_name,s.s_birthday,s.s_class, c.c_no, c.c_name, sc.sc_degree , t.t_name FROM student AS s, course AS c, score AS sc,teacher AS t WHERE  s.s_class IN('95031','95033') AND s.s_no = sc.s_no AND sc.c_no = c.c_no AND c.t_no = t.t_no;
    +------+--------+---------------------+---------+-------+------------+-----------+--------+
    | s_no | s_name | s_birthday          | s_class | c_no  | c_name     | sc_degree | t_name |
    +------+--------+---------------------+---------+-------+------------+-----------+--------+
    | 102  | 匡明   | 1975-10-02 00:00:00 | 95031   | 3-105 | 计算机导论 |        91 | 王萍   |
    | 105  | 王芳   | 1975-02-10 00:00:00 | 95031   | 3-105 | 计算机导论 |        88 | 王萍   |
    | 105  | 王芳   | 1975-02-10 00:00:00 | 95031   | 3-245 | 操作系统   |        75 | 李诚   |
    | 105  | 王芳   | 1975-02-10 00:00:00 | 95031   | 6-166 | 数字电路   |        79 | 张旭   |
    | 109  | 赵铁柱 | 1974-06-03 00:00:00 | 95031   | 3-105 | 计算机导论 |        76 | 王萍   |
    | 109  | 赵铁柱 | 1974-06-03 00:00:00 | 95031   | 3-245 | 操作系统   |        68 | 李诚   |
    | 109  | 赵铁柱 | 1974-06-03 00:00:00 | 95031   | 6-166 | 数字电路   |        81 | 张旭   |
    | 101  | 曾华   | 1977-09-01 00:00:00 | 95033   | 3-105 | 计算机导论 |        90 | 王萍   |
    | 103  | 王丽   | 1976-01-23 00:00:00 | 95033   | 3-105 | 计算机导论 |        92 | 王萍   |
    | 103  | 王丽   | 1976-01-23 00:00:00 | 95033   | 3-245 | 操作系统   |        86 | 李诚   |
    | 103  | 王丽   | 1976-01-23 00:00:00 | 95033   | 6-166 | 数字电路   |        85 | 张旭   |
    | 104  | 李军   | 1976-02-20 00:00:00 | 95033   | 3-105 | 计算机导论 |        89 | 王萍   |
    +------+--------+---------------------+---------+-------+------------+-----------+--------+

– 24.查询存在85分以上成绩的课程c\_no

SELECT * FROM score where sc_degree > 85;
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 101  | 3-105 |        90 |
    | 102  | 3-105 |        91 |
    | 103  | 3-105 |        92 |
    | 103  | 3-245 |        86 |
    | 104  | 3-105 |        89 |
    | 105  | 3-105 |        88 |
    +------+-------+-----------+
    
    升级版:知道c_no还不行,我们还需要看到c_name 以及对应的老师
    SELECT sc.c_no,c.c_name, t.t_name FROM score AS sc, course AS c, teacher AS t WHERE sc.c_no IN(SELECT c_no FROM score where sc_degree > 85) AND sc.c_no = c.c_no AND c.t_no = t.t_no GROUP BY c.c_name;
    +-------+------------+--------+
    | c_no  | c_name     | t_name |
    +-------+------------+--------+
    | 3-105 | 计算机导论 | 王萍   |
    | 3-245 | 操作系统   | 李诚   |
    +-------+------------+--------+
    这两位老师教出来的学生都有85分以上的

– 25.查出所有’计算机系’ 教师所教课程的成绩表

SELECT * FROM score WHERE c_no IN (SELECT c_no FROM course WHERE t_no IN (SELECT t_no FROM teacher WHERE t_depart = '计算机系'));
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 103  | 3-245 |        86 |
    | 105  | 3-245 |        75 |
    | 109  | 3-245 |        68 |
    | 101  | 3-105 |        90 |
    | 102  | 3-105 |        91 |
    | 103  | 3-105 |        92 |
    | 104  | 3-105 |        89 |
    | 105  | 3-105 |        88 |
    | 109  | 3-105 |        76 |
    +------+-------+-----------+
    
    进阶:
    SELECT  t.t_name,t.t_depart,c.c_name,s.s_name,s_class,sc.sc_degree FROM course AS c, score AS sc, teacher AS t,student AS s WHERE c.t_no IN (select t_no FROM teacher WHERE t_depart = '计算机系') AND c.t_no = t.t_no AND c.c_no = sc.c_no AND sc.s_no = s.s_no ;
     教师名称  部门        课程名称      学生名称  班级        分数
    +--------+----------+------------+--------+---------+-----------+
    | t_name | t_depart | c_name     | s_name | s_class | sc_degree |
    +--------+----------+------------+--------+---------+-----------+
    | 李诚   | 计算机系 | 操作系统   | 王丽   | 95033   |        86 |
    | 李诚   | 计算机系 | 操作系统   | 王芳   | 95031   |        75 |
    | 李诚   | 计算机系 | 操作系统   | 赵铁柱 | 95031   |        68 |
    | 王萍   | 计算机系 | 计算机导论 | 曾华   | 95033   |        90 |
    | 王萍   | 计算机系 | 计算机导论 | 匡明   | 95031   |        91 |
    | 王萍   | 计算机系 | 计算机导论 | 王丽   | 95033   |        92 |
    | 王萍   | 计算机系 | 计算机导论 | 李军   | 95033   |        89 |
    | 王萍   | 计算机系 | 计算机导论 | 王芳   | 95031   |        88 |
    | 王萍   | 计算机系 | 计算机导论 | 赵铁柱 | 95031   |        76 |
    +--------+----------+------------+--------+---------+-----------+

– 26.查询’计算机系’与’电子工程系’ 不同职称的教师的name和rof

SELECT * FROM teacher WHERE t_depart = '计算机系' AND t_rof NOT IN (SELECT t_rof FROM teacher WHERE t_depart = '电子工程系')
    UNION
    SELECT * FROM teacher WHERE t_depart = '电子工程系' AND t_rof NOT IN (SELECT t_rof FROM teacher WHERE t_depart = '计算机系');
    
    +------+--------+-------+---------------------+--------+------------+
    | t_no | t_name | t_sex | t_birthday          | t_rof  | t_depart   |
    +------+--------+-------+---------------------+--------+------------+
    | 804  | 李诚   | 男    | 1958-12-02 00:00:00 | 副教授 | 计算机系   |
    | 856  | 张旭   | 男    | 1969-03-12 00:00:00 | 讲师   | 电子工程系 |
    +------+--------+-------+---------------------+--------+------------+

– 27, 查询选修编号为"3-105"课程且成绩至少高于选修编号为’3-245’同学的c\_no,s\_no和

sc_degree,并且按照sc_degree从高到地次序排序
    select * from score where c_no = '3-105' AND sc_degree > ANY(SELECT sc_degree FROM score WHERE c_no = '3-245' ) ORDER BY sc_degree desc ;
    
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 103  | 3-105 |        92 |
    | 102  | 3-105 |        91 |
    | 101  | 3-105 |        90 |
    | 104  | 3-105 |        89 |
    | 105  | 3-105 |        88 |
    | 109  | 3-105 |        76 |
    +------+-------+-----------+

– 28.查询选修编号为"3-105"且成绩高于选修编号为"3-245"课程的同学c\_no.s\_no和sc\_degree

SELECT * FROM score WHERE sc_degree > ALL (select sc_degree from score WHERE c_no = '3-245') AND c_no = '3-105';
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 101  | 3-105 |        90 |
    | 102  | 3-105 |        91 |
    | 103  | 3-105 |        92 |
    | 104  | 3-105 |        89 |
    | 105  | 3-105 |        88 |
    +------+-------+-----------+
    
    进阶:查出学生的信息,课程名称,分数(s_name c_name,sc_degree)
    SELECT s.s_name , c.c_name ,sc.sc_degree FROM score AS sc, student AS s,course AS c WHERE sc_degree > ALL (select sc_degree from score WHERE c.c_no = '3-245') AND c.c_no = '3-105' AND sc.s_no = s.s_no AND sc.c_no = c.c_no ;
    +--------+------------+-----------+
    | s_name | c_name     | sc_degree |
    +--------+------------+-----------+
    | 曾华   | 计算机导论 |        90 |
    | 匡明   | 计算机导论 |        91 |
    | 王丽   | 计算机导论 |        92 |
    | 李军   | 计算机导论 |        89 |
    | 王芳   | 计算机导论 |        88 |
    | 赵铁柱 | 计算机导论 |        76 |
    +--------+------------+-----------+
    总结: ANY 和 ALL
    ANY:表示任何一个就行了,如;数组A中的值比数组B中任何一个都要大,那么只要A和B中最小的比较就行了.
    ALL:表示所有都要比较,如:数组A中的值比数组B中所有的数都要大,那么A要和B中最大的值比较才行.

– 29. 查询所有教师和同学的 name ,sex, birthday

SELECT s_name AS name, s_sex AS sex, s_birthday AS birthday  FROM student
    UNION
    SELECT t_name AS name, t_sex AS sex, t_birthday AS birthday FROM teacher;
    +--------+-----+---------------------+
    | name   | sex | birthday            |
    +--------+-----+---------------------+
    | 曾华   | 男  | 1977-09-01 00:00:00 |
    | 匡明   | 男  | 1975-10-02 00:00:00 |
    | 王丽   | 女  | 1976-01-23 00:00:00 |
    | 李军   | 男  | 1976-02-20 00:00:00 |
    | 王芳   | 女  | 1975-02-10 00:00:00 |
    | 陆军   | 男  | 1974-06-03 00:00:00 |
    | 王尼玛 | 男  | 1976-02-20 00:00:00 |
    | 张全蛋 | 男  | 1975-02-10 00:00:00 |
    | 赵铁柱 | 男  | 1974-06-03 00:00:00 |
    | 张飞   | 男  | 1974-06-03 00:00:00 |
    | 李诚   | 男  | 1958-12-02 00:00:00 |
    | 王萍   | 女  | 1972-05-05 00:00:00 |
    | 刘冰   | 女  | 1977-08-14 00:00:00 |
    | 张旭   | 男  | 1969-03-12 00:00:00 |
    +--------+-----+---------------------+

– 30.查询所有’女’教师和’女’学生的name,sex,birthday

SELECT s_name AS name, s_sex AS sex, s_birthday AS birthday  FROM student WHERE s_sex = '女'
    UNION
    SELECT t_name AS name, t_sex AS sex, t_birthday AS birthday FROM teacher WHERE t_sex = '女';
    +------+-----+---------------------+
    | name | sex | birthday            |
    +------+-----+---------------------+
    | 王丽 | 女  | 1976-01-23 00:00:00 |
    | 王芳 | 女  | 1975-02-10 00:00:00 |
    | 王萍 | 女  | 1972-05-05 00:00:00 |
    | 刘冰 | 女  | 1977-08-14 00:00:00 |
    +------+-----+---------------------+

– 31.查询成绩比该课程平均成绩低的同学的成绩表

score:
    +------+-------+-----------+    
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 101  | 3-105 |        90 |
    | 102  | 3-105 |        91 |
    | 103  | 3-105 |        92 |
    | 103  | 3-245 |        86 |
    | 103  | 6-166 |        85 |
    | 104  | 3-105 |        89 |
    | 105  | 3-105 |        88 |
    | 105  | 3-245 |        75 |
    | 105  | 6-166 |        79 |
    | 109  | 3-105 |        76 |
    | 109  | 3-245 |        68 |
    | 109  | 6-166 |        68 |    我数据库中:    109  | 6-166 |        81
    +------+-------+-----------+
    
    SELECT * FROM score AS sc1 WHERE sc1.sc_degree < (SELECT  AVG(sc_degree) FROM score AS sc2 WHERE sc1.c_no = sc2.c_no);
    +------+-------+-----------+  
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 105  | 3-245 |        75 |
    | 105  | 6-166 |        79 |
    | 109  | 3-105 |        76 |
    | 109  | 3-245 |        68 |
    | 109  | 6-166 |        81 |
    +------+-------+-----------+
    
    进阶,显示出学生name,课程name以及分数
    SELECT s.s_name ,sc1.c_no,c.c_name, sc1.sc_degree FROM score AS sc1,student AS s,course AS c WHERE sc1.sc_degree < (SELECT  AVG(sc_degree) FROM score AS sc2 WHERE sc1.c_no = sc2.c_no) AND sc1.s_no = s.s_no AND sc1.c_no = c.c_no ;
    +--------+-------+------------+-----------+
    | s_name | c_no  | c_name     | sc_degree |
    +--------+-------+------------+-----------+
    | 赵铁柱 | 3-105 | 计算机导论 |        76 |
    | 王芳   | 3-245 | 操作系统   |        75 |
    | 赵铁柱 | 3-245 | 操作系统   |        68 |
    | 王芳   | 6-166 | 数字电路   |        79 |
    | 赵铁柱 | 6-166 | 数字电路   |        81 |
    +--------+-------+------------+-----------+

– 32.查询所有任课教师的t\_name 和 t\_depart(要在分数表中可以查得到)

SELECT * FROM teacher WHERE t_no IN(SELECT t_no FROM course);
    +------+--------+-------+---------------------+--------+------------+
    | t_no | t_name | t_sex | t_birthday          | t_rof  | t_depart   |
    +------+--------+-------+---------------------+--------+------------+
    | 804  | 李诚   | 男    | 1958-12-02 00:00:00 | 副教授 | 计算机系   |
    | 825  | 王萍   | 女    | 1972-05-05 00:00:00 | 助教   | 计算机系   |
    | 831  | 刘冰   | 女    | 1977-08-14 00:00:00 | 助教   | 电子工程系 |
    | 856  | 张旭   | 男    | 1969-03-12 00:00:00 | 讲师   | 电子工程系 |
    +------+--------+-------+---------------------+--------+------------+

注意:我个人是从score表中查出有过考试成绩的课程,再用该课程查出教师的,因为当时我个人认为只有有考试成绩才算"任课",既然我写出来了,那我就放出来:(根据具体业务)

SELECT * FROM teacher WHERE t_no IN(SELECT t_no FROM course WHERE c_no IN (SELECT c_no from score));
    +------+--------+-------+---------------------+--------+------------+
    | t_no | t_name | t_sex | t_birthday          | t_rof  | t_depart   |
    +------+--------+-------+---------------------+--------+------------+
    | 804  | 李诚   | 男    | 1958-12-02 00:00:00 | 副教授 | 计算机系   |
    | 825  | 王萍   | 女    | 1972-05-05 00:00:00 | 助教   | 计算机系   |
    | 856  | 张旭   | 男    | 1969-03-12 00:00:00 | 讲师   | 电子工程系 |
    +------+--------+-------+---------------------+--------+------------+

– 33.查出至少有2名男生的班号

SELECT s_class FROM student WHERE s_sex = '男' GROUP BY s_class HAVING COUNT(s_no) > 1; 
    +---------+
    | s_class |
    +---------+
    | 95033   |
    | 95031   |
    +---------+

– 34.查询student 表中 不姓"王"的同学的记录

SELECT * FROM student WHERE s_name NOT LIKE '王%'; 
    +------+--------+-------+---------------------+---------+
    | s_no | s_name | s_sex | s_birthday          | s_class |
    +------+--------+-------+---------------------+---------+
    | 101  | 曾华   | 男    | 1977-09-01 00:00:00 | 95033   |
    | 102  | 匡明   | 男    | 1975-10-02 00:00:00 | 95031   |
    | 104  | 李军   | 男    | 1976-02-20 00:00:00 | 95033   |
    | 106  | 陆军   | 男    | 1974-06-03 00:00:00 | 95031   |
    | 108  | 张全蛋 | 男    | 1975-02-10 00:00:00 | 95031   |
    | 109  | 赵铁柱 | 男    | 1974-06-03 00:00:00 | 95031   |
    | 110  | 张飞   | 男    | 1974-06-03 00:00:00 | 95038   |
    +------+--------+-------+---------------------+---------+

– 35. 查询student 中每个学生的姓名和年龄(当前时间 - 出生年份)

SELECT s_name, YEAR(NOW()) - YEAR(s_birthday) AS age FROM student;
    +--------+------+
    | s_name | age  |
    +--------+------+
    | 曾华   |   42 |
    | 匡明   |   44 |
    | 王丽   |   43 |
    | 李军   |   43 |
    | 王芳   |   44 |
    | 陆军   |   45 |
    | 王尼玛 |   43 |
    | 张全蛋 |   44 |
    | 赵铁柱 |   45 |
    | 张飞   |   45 |
    +--------+------+

– 36. 查询student中最大和最小的 s\_birthday的值

SELECT MAX(s_birthday),MIN(s_birthday) FROM student;
    +---------------------+---------------------+
    | MAX(s_birthday)     | MIN(s_birthday)     |
    +---------------------+---------------------+
    | 1977-09-01 00:00:00 | 1974-06-03 00:00:00 |
    +---------------------+---------------------+

– 37.以班级号和年龄从大到小的顺序查询student表中的全部记录

SELECt * FROM student ORDER BY s_class DESC, s_birthday; 
    +------+--------+-------+---------------------+---------+
    | s_no | s_name | s_sex | s_birthday          | s_class |
    +------+--------+-------+---------------------+---------+
    | 110  | 张飞   | 男    | 1974-06-03 00:00:00 | 95038   |
    | 103  | 王丽   | 女    | 1976-01-23 00:00:00 | 95033   |
    | 104  | 李军   | 男    | 1976-02-20 00:00:00 | 95033   |
    | 107  | 王尼玛 | 男    | 1976-02-20 00:00:00 | 95033   |
    | 101  | 曾华   | 男    | 1977-09-01 00:00:00 | 95033   |
    | 106  | 陆军   | 男    | 1974-06-03 00:00:00 | 95031   |
    | 109  | 赵铁柱 | 男    | 1974-06-03 00:00:00 | 95031   |
    | 105  | 王芳   | 女    | 1975-02-10 00:00:00 | 95031   |
    | 108  | 张全蛋 | 男    | 1975-02-10 00:00:00 | 95031   |
    | 102  | 匡明   | 男    | 1975-10-02 00:00:00 | 95031   |
    +------+--------+-------+---------------------+---------+

– 38.查询"男"教师 及其所上的课

SELECT * FROM course WHERE t_no IN (SELECT t_no FROM teacher WHERE t_sex = '男');
    +-------+----------+------+
    | c_no  | c_name   | t_no |
    +-------+----------+------+
    | 3-245 | 操作系统 | 804  |
    | 6-166 | 数字电路 | 856  |
    +-------+----------+------+
    
    进阶:查出教师名称,教师性别, 课程名字
    SELECT t.t_name,t.t_sex ,c.c_name FROM teacher t ,course c WHERE t_sex = '男' AND t.t_no = c.t_no;
    +--------+-------+----------+
    | t_name | t_sex | c_name   |
    +--------+-------+----------+
    | 李诚   | 男    | 操作系统 |
    | 张旭   | 男    | 数字电路 |
    +--------+-------+----------+

– 39.查询最高分同学的s\_no c\_no 和 sc\_degree;

SELECT * FROM score WHERE sc_degree = (select MAX(sc_degree) AS sc_degree FROM score);
    
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 103  | 3-105 |        92 |
    +------+-------+-----------+

– 40. 查询和"李军"同性别的所有同学的s\_name

SELECT s_name, s_sex FROM student WHERE s_SEX = (SELECT s_sex FROM student WHERE s_name = '李军');
    
    +--------+-------+
    | s_name | s_sex |
    +--------+-------+
    | 曾华   | 男    |
    | 匡明   | 男    |
    | 李军   | 男    |
    | 陆军   | 男    |
    | 王尼玛 | 男    |
    | 张全蛋 | 男    |
    | 赵铁柱 | 男    |
    | 张飞   | 男    |
    +--------+-------+

– 41.查询和"李军"同性别并且同班的所有同学的s\_name

SELECT s_name, s_sex FROM student WHERE s_sex = (SELECT s_sex FROM student WHERE s_name = '李军') AND s_class = (SELECT s_class FROM student WHERE s_name = '李军');
    +--------+-------+
    | s_name | s_sex |
    +--------+-------+
    | 曾华   | 男    |
    | 李军   | 男    |
    | 王尼玛 | 男    |
    +--------+-------+
    
    SELECT s_name, s_sex FROM student s1 WHERE s_sex = (SELECT s_sex FROM student s2 WHERE s_name = '李军' AND s1.s_class = s2.s_class);
    +--------+-------+
    | s_name | s_sex |
    +--------+-------+
    | 曾华   | 男    |
    | 李军   | 男    |
    | 王尼玛 | 男    |
    +--------+-------+

– 42. 查询所有选修’计算机导论’课程的’男’同学的成绩表

SELECT * FROM score WHERE c_no = (SELECT c_no FROM course WHERE c_name = '计算机导论' ) AND s_no IN(SELECT s_no FROM student WHERE s_sex = '男');
    
    +------+-------+-----------+
    | s_no | c_no  | sc_degree |
    +------+-------+-----------+
    | 101  | 3-105 |        90 |
    | 102  | 3-105 |        91 |
    | 104  | 3-105 |        89 |
    | 109  | 3-105 |        76 |
    +------+-------+-----------+
    
    进阶:显示出s_name,c_name 替代之前的 s_no and c_no
    SELECT s_name,c_name,sc_degree FROM score,student,course WHERE score.c_no = (SELECT c_no FROM course WHERE c_name = '计算机导论' ) AND score.s_no IN(SELECT s_no FROM student WHERE s_sex = '男') AND score.s_no = student.s_no AND score.c_no = course.c_no ;
    +--------+------------+-----------+
    | s_name | c_name     | sc_degree |
    +--------+------------+-----------+
    | 曾华   | 计算机导论 |        90 |
    | 匡明   | 计算机导论 |        91 |
    | 李军   | 计算机导论 |        89 |
    | 赵铁柱 | 计算机导论 |        76 |
    +--------+------------+-----------+

– 43. 假设使用了以下命令建立了一个grade表

CREATE TABLE grade(
        low INT(3),
        upp INT(3),
        grade CHAR(1)
    );
    INSERT INTO grade VALUES(90,100,'A');
    INSERT INTO grade VALUES(80,89,'B');
    INSERT INTO grade VALUES(70,79,'c');
    INSERT INTO grade VALUES(60,69,'D');
    INSERT INTO grade VALUES(0,59,'E');
    -- 查询所有同学的s_no , c_no 和grade列
    SELECT s_no, c_no , grade FROM score, grade WHERE sc_degree BETWEEN low and upp; 
    +------+-------+-------+
    | s_no | c_no  | grade |
    +------+-------+-------+
    | 101  | 3-105 | A     |
    | 102  | 3-105 | A     |
    | 103  | 3-105 | A     |
    | 103  | 3-245 | B     |
    | 103  | 6-166 | B     |
    | 104  | 3-105 | B     |
    | 105  | 3-105 | B     |
    | 105  | 3-245 | c     |
    | 105  | 6-166 | c     |
    | 109  | 3-105 | c     |
    | 109  | 3-245 | D     |
    | 109  | 6-166 | B     |
    +------+-------+-------+
    
    进阶:显示学生名字和课程名称
    SELECT  s.s_no, s.s_name, c.c_name ,c.c_no , grade FROM student s, course c ,score sc, grade WHERE sc_degree BETWEEN low and upp AND sc.s_no = s.s_no AND sc.c_no = c.c_no;
    +------+--------+------------+-------+-------+
    | s_no | s_name | c_name     | c_no  | grade |
    +------+--------+------------+-------+-------+
    | 101  | 曾华   | 计算机导论 | 3-105 | A     |
    | 102  | 匡明   | 计算机导论 | 3-105 | A     |
    | 103  | 王丽   | 计算机导论 | 3-105 | A     |
    | 103  | 王丽   | 操作系统   | 3-245 | B     |
    | 103  | 王丽   | 数字电路   | 6-166 | B     |
    | 104  | 李军   | 计算机导论 | 3-105 | B     |
    | 105  | 王芳   | 计算机导论 | 3-105 | B     |
    | 105  | 王芳   | 操作系统   | 3-245 | c     |
    | 105  | 王芳   | 数字电路   | 6-166 | c     |
    | 109  | 赵铁柱 | 计算机导论 | 3-105 | c     |
    | 109  | 赵铁柱 | 操作系统   | 3-245 | D     |
    | 109  | 赵铁柱 | 数字电路   | 6-166 | B     |
    +------+--------+------------+-------+-------+