授業メモ
SELECT country.cname, country.population, river.rname, river.len, mount.mname, mount.elevation FROM country, river, mount, mhold, rhold WHERE country.population > 50000 AND mount.elevation > 4000 AND river.len > 1000 AND country.cname = mhold.cname AND mhold.mname = mount.mname AND country.cname = rhold.cname AND rhold.rname = river.rname;