CREATE TABLE host (host_id NUMBER, name CLOB, nationality CLOB, age CLOB)
CREATE TABLE party_host (party_id NUMBER, host_id NUMBER, is_main_in_charge others)
CREATE TABLE party (party_id NUMBER, party_theme CLOB, location CLOB, first_year CLOB, last_year CLOB, number_of_hosts NUMBER)

Which nations have both hosts of age above 45 and hosts of age below 35?
SELECT nationality FROM host WHERE age > 45 INTERSECT SELECT nationality FROM host WHERE age < 35
SELECT "nationality" FROM "host" WHERE "age" > 45 INTERSECT SELECT "nationality" FROM "host" WHERE "age" < 35