What are the id of students who registered courses or attended courses?
SELECT student_id FROM student_course_registrations UNION SELECT student_id FROM student_course_attendance
SELECT student_id FROM student_course_registrations UNION SELECT student_id FROM student_course_attendance
[{'student_id': 111}, {'student_id': 121}, {'student_id': 131}, {'student_id': 141}, {'student_id': 151}, {'student_id': 161}, {'student_id': 171}]