SELECT count(*) ,  class_room FROM CLASS GROUP BY class_room HAVING count(*)  >=  2
For each classroom with at least 2 classes, how many classes are offered?
SELECT count ( * ) , class_room FROM CLASS GROUP BY class_room HAVING count ( * ) > = 2
select count ( * ) , class_room from class group by class_room having count ( * ) > = value
For each classroom with at least 2 classes , how many classes are offered ?