SQL || MySQL ||作者：穆尼塞卡·乌达瓦拉帕蒂

create table class(
    class_id int primary key,
    class_name varchar(50),
    foreign key (teacher_id) references teacher(teacher_id)
);

create table teacher (
    teacher_id int primary key,
    teacher_name varchar(100),
    age int,
    subject varchar(50),
    experience int
);

insert into teacher(teacher_id,teacher_name,age,subject,experience)
values
(101, 'sk. sohana', 30, 'mathematics', 5),
(102, 'u. munisekhar', 35, 'english', 8),
(103, 'sk. nellu', 40, 'science', 10),
(104, 'a. venu', 28, 'history', 3);

insert into class(class_id,class_name,teacher_id)
(9, 'math', 101),
(10, 'english', 102),
(11, 'science', 103),
(12, 'history', 104);

select * from class;

| class_id | class_name         | teacher_id |
|----------|--------------------|------------|
| 9        | math               | 101        |
| 10       | english            | 102        |
| 11       | science            | 103        |
| 12       | history            | 104        |

select * from teacher whare experience >5

| teacher_id | teacher_name       | age | subject       | experience |
|------------|--------------------|-----|---------------|------------|
| 102        | u. munisekhar      | 35  | english       | 8          |
| 103        | sk. nellu          | 40  | science       | 10         |

select * from teacher where teacher_name='u. munisekhar'

| teacher_id | teacher_name       | age | subject       | experience |
|------------|--------------------|-----|---------------|------------|
| 102        | u. munisekhar      | 35  | english       | 8          |

select experience from teacher where teacher_name='sk. sohana';

| experience |
|------------|
|     8      |

select name,age from teacher where age between 29 and 39;

| teacher_name       | age |
|--------------------|-----|
| sk. sohana         | 30  | 
| u. munisekhar      | 35  | 

select class.class_name, teacher.teacher_name
from class
right join teacher on class.teacher_id=teacher.teacher_id;

| class_name | teacher_name       |
|------------|--------------------|
| math       | sk. sohana         |
| english    | u. munisekhar      |
| science    | sk. nellu          |
| history    | a. venu            |

select class.class_name, teacher.teacher_name
from class
right join teacher on class.teacher_id=teacher.teacher_id;

| class_name | teacher_name       |
|------------|--------------------|
| math       | sk. sohana         |
| english    | u. munisekhar      |
| science    | sk. nellu          |
| history    | a. venu            |
| null       | s. jagadeesh       |

select class.class_name, teacher.teacher_name
from class
inner join teacher on class.teacher_id=teacher.teacher_id;

| class_name | teacher_name       |
|------------|--------------------|
| math       | sk. sohana         |
| english    | u. munisekhar      |
| science    | sk. nellu          |
| history    | a. venu            |

select teacher.teacher.name, class.class_name
from teacher 
right join class on teacher.teacher_id=class.teacher_id
where teacher.teacher_name = 'u. munisekhar';

| teacher_name       | class_name |
|--------------------|------------|
| U. Munisekhar      | English    |