How many countries have more than one roller coaster?
select count ( * )  from  ( SELECT T1.Name FROM country AS T1 JOIN roller_coaster AS T2 ON T1.Country_ID   =   T2.Country_ID GROUP BY T1.Name HAVING COUNT ( * )   >  1 ) 
counting countries with more than one roller coaster refers to COUNT(*) with GROUP BY and HAVING COUNT(*) > 1;