query: SELECT student_id FROM student_course_registrations UNION SELECT student_id FROM student_course_attendance
question: What id student who had registered course or attended course?
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 id student who had registered course or attended course?