= UseCase3001Implementation – Enroll in Subject

**Initiating actor:** Student

**Other actors:** None

**Description:** Student enrolls in a subject offered by their faculty and selects a specific professor teaching that course instance.

**Scenario:**

1. System displays Student Menu.

2. Student selects Enroll in Subject.

3. System lists all students → Student selects their Student ID.

4. System lists available subjects for the student's faculty:
{{{
SELECT s.Id, s.Name 
FROM Subject s 
JOIN Student st ON s.Faculty_Id = st.Faculty_Id 
WHERE st.Id = ?;
}}}
Student selects a Subject ID.

5. System lists all available professors for the chosen subject:
{{{
SELECT p.Id, p.Name, p.Surname 
FROM Professor p 
JOIN Subject s ON p.Faculty_Id = s.Faculty_Id 
WHERE s.Id = ?;
}}}
Student selects a Professor ID.

6. System checks if the student is already enrolled in this subject:
{{{
SELECT * FROM Student_Subject WHERE Student_Id = ? AND Subject_Id = ?;
}}}

7. If not enrolled, system inserts the new enrollment record into the database:
{{{
INSERT INTO Student_Subject(Student_Id, Subject_Id, Professor_Id, Status, Enrollment_Date, Absences_Count)
VALUES (?, ?, ?, 'PASSED', CURRENT_DATE, 0);
}}}

8. System confirms successful enrollment.

[[Image(enrollSubject1.png, 800px)]]
[[Image(enrollSubject2.png, 800px)]]
[[Image(enrollSubject3.png, 800px)]]
[[Image(enrollSubject4.png, 800px)]]