In this lab, student S209 has an advisor row with no advisor yet (i_id is NULL). A new instructor, Ruth Abara, has no department yet (dept_name is NULL).

1. The names of the students who take no course.
2. Think before you run it: how many rows does this query return?

SELECT name FROM instructor
WHERE id NOT IN (SELECT i_id FROM advisor);

3. The names of the instructors who advise nobody.
4. The names of the departments (dept_name) that have no instructor.