= UC3001 – Enroll in Subject Implementation 

'''Initiating actor:''' Student
'''Other actors:''' None

'''Description:''' 
Student registers for an available course module matching their faculty division and selects an associated professor who oversees that course instance.

'''Scenario:'''
1. System displays the Student Menu interface.
2. Student selects the option to "Enroll in Subject".
3. System outputs a full list of registered students, and the user selects their unique Student ID.
4. System identifies the student's faculty association and filters all valid available subjects:
{{{
SELECT s.Id, s.Name 
FROM Subject s 
JOIN Student st ON s.Faculty_Id = st.Faculty_Id 
WHERE st.Id = ?;
}}}
Student selects a target Subject ID from the listing.

5. System queries and displays all professors affiliated with the faculty offering that selected 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 specific Professor ID.

6. System performs an validation check to ensure a duplicate active enrollment does not already exist:
{{{
SELECT * FROM Student_Subject WHERE Student_Id = ? AND Subject_Id = ?;
}}}
7. If no prior enrollment is found, the system saves the record using the baseline registration status:
{{{
INSERT INTO Student_Subject (Student_Id, Subject_Id, Professor_Id, Status, Enrollment_Date, Absences_Count)
VALUES (?, ?, ?, 'Enrolled', CURRENT_DATE, 0);
}}}
8. System prints a terminal message confirming that course enrollment completed successfully.

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