query: SELECT student_id FROM student_course_registrations UNION SELECT student_id FROM student_course_attendance
question: What-all are the id of students who register courses or a-attended courses?
query_toks: SELECT student_id FROM student_course_registrations UNION SELECT student_id FROM student_course_attendance
query_toks_no_value: select student_id from student_course_registrations union select student_id from student_course_attendance
question_toks: What-all are the id of students who register courses or a-attended courses?