## Difficulty_Level

ID | Level
--- | ---
1 | Beginner
2 | Advanced
3 | Expert

## Subjects

ID | Name | Description | DifficultyID
--- | --- | --- | ---
|  |  | (→ Difficulty_Level.ID)
1 | Math | Introduction to Mathematics | 1
2 | Physics | Basic Principles of Physics | 2
3 | Biology | Basics of Biological Sciences | 3
4 | History | World History Overview | 1
5 | Literature | Classic Novels Analysis | 2

## Textbooks

ID | Title | Author | ISBN | SubjectID
--- | --- | --- | --- | ---
|  |  |  | (→ Subjects.ID)
1 | Mathematics for Beginners | John Doe | 978-0-123-456789 | 1
2 | The World of Physics | Jane Smith | 978-0-091-234567 | 2
3 | An Introduction to Biology | Michael Brown | 978-1-234-567890 | 3
4 | A Brief History of Time | Stephen Hawking | 978-0-123-987654 | 4
5 | To Kill a Mockingbird | Harper Lee | 978-0-123-123456 | 5

## Online_Courses

ID | CourseName | Instructor | Platform | URL | SubjectID
--- | --- | --- | --- | --- | ---
|  |  |  |  | (→ Subjects.ID)
1 | Introductory Math | Prof. James Johnson | Udemy | https://www.udemy.com/introductory-math | 1
2 | Essential Physics | Dr. Emily White | Coursera | https://www.coursera.org/physics | 2
3 | Foundations of Biology | Dr. Robert Green | edX | https://www.edx.org/biology | 3
4 | Global History Survey | Dr. Susan King | FutureLearn | https://www.futurelearn.com/history | 4
5 | Great Literary Works | Ms. Karen Taylor | LinkedIn Learning | https://www.linkedinlearning.com/literature | 5

## EnrolledStudents

StudentID | FirstName | LastName | Age | Email | PhoneNumber | IsEnrolledInTextbook | IsEnrolledInOnlineCourse
--- | --- | --- | --- | --- | --- | --- | ---
1 | Alice | Smith | 20 | alicesmith@example.com | +1-123-456-7890 | 1 | 0
2 | Bob | Johnson | 21 | bobjohnson@example.com | +1-987-654-3210 | 0 | 1
3 | Charlie | Williams | 22 | charliewilliams@example.com | +1-555-123-4567 | 1 | 1
4 | David | Martinez | 23 | davidmartinez@example.com | +1-321-654-9870 | 0 | 0
5 | Eva | Garcia | 24 | evagarcia@example.com | +1-789-456-1234 | 1 | 0