mysql查询练习

新建一个查询用的数据库selectTest:

DATABASE selectTest;```

选择该数据库：

```USE selectTest;

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 COMMNET'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'学生所在班级'
);

课程表：
course
课程号
课程名称
教师编号

CREATE TABLE course(
    c_no VARCHAR(20) PRIMARY KEY COMMENT'课程号',
    c_name VACHAR(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) reference teacher(t_no)
);

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

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

SHOW TABLES;
+----------------------+
| Tables_in_selecttest |
+----------------------+
| course               |
| score                |
| student              |
| teacher              |
+----------------------+

查看student表结构    DESCRIBE student;
+------------+-------------+------+-----+---------+-------+
| Field      | Type        | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+-------+
| s_no       | varchar(20) | NO   | PRI | NULL    |       |
| s_name     | varchar(20) | NO   |     | NULL    |       |
| s_sex      | varchar(10) | NO   |     | NULL    |       |
| s_birthday | datetime    | YES  |     | NULL    |       |
| s_class    | varchar(20) | YES  |     | NULL    |       |
+------------+-------------+------+-----+---------+-------+

查看teacher表结构    DESCRIBE teacher;
+------------+-------------+------+-----+---------+-------+
| Field      | Type        | Null | Key | Default | Extra |
+------------+-------------+------+-----+---------+-------+
| t_no       | varchar(20) | NO   | PRI | NULL    |       |
| t_name     | varchar(20) | NO   |     | NULL    |       |
| t_sex      | varchar(20) | NO   |     | NULL    |       |
| t_birthday | datetime    | YES  |     | NULL    |       |
| t_rof      | varchar(20) | NO   |     | NULL    |       |
| t_depart   | varchar(20) | NO   |     | NULL    |       |
+------------+-------------+------+-----+---------+-------+

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

SELECT distinct (t_depart) FROM teacher; 
+------------+
| t_depart   |
+------------+
| 计算机系   |
| 计算机机系 |
| 电子工程系 |
+------------+


-- 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 |
+------+-------+-----------+

不过视频中仅仅查出来了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   |
+------+--------+-------+---------------------+---------+

由于视频中就只有这两个班,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
注意:我的数据和视频中的数据有点不一样,所以查询结果有点区别
视频中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     |
+------+--------+------------+-------+-------+