Hello!  Can you show me a list of all course IDs?
select course_id from takes
Wow that's a lot!  Can you update that list to show me the semester and year which have the fewest number of students taking any class?
select semester, year from takes group by semester, year order by count ( * ) limit 1
Yes!  That is what I meant!  Sorry!  How many total classes were taken in Fall of 2008?
select count ( * ) from takes where semester = 'Fall' and year = '2008'