text: Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
  ### Context:
  CREATE TABLE student_course_attendance (course_id VARCHAR, student_id VARCHAR); CREATE TABLE student_course_registrations (course_id VARCHAR, student_id VARCHAR)
  ### Question:
  Find the id of courses which are registered or attended by student whose id is 121?
  ### Answer:
  SELECT course_id FROM student_course_registrations WHERE student_id = 121 UNION SELECT course_id FROM student_course_attendance WHERE student_id = 121