SELECT count(*) FROM (SELECT city FROM airports GROUP BY city HAVING count(*)  >  3)
How many cities are there that have more than 3 airports?
SELECT count ( * ) FROM ( SELECT city FROM airports GROUP BY city HAVING count ( * ) > 3 )
select count ( * ) from ( select city from airports group by city having count ( * ) > value )
How many cities are there that have more than 3 airports ?