How many buildings are in the list?
select count ( distinct building ) from classroom
What are the buildings that have more than 50 capacity?
select building from classroom where capacity > 50 group by building
Can you rind me the number of rooms with more than 50 capacity for those 20 buildings?
select count ( room_number ) from classroom where capacity > 50
Can you show me the number of rooms with capacity greater than 50 for each building?
select building, count ( room_number ) from classroom where capacity > 50 group by building