Show all cities where at least one customer lives in but no performer lives in.
create table customers (address_id varchar, PRIMARY KEY (address_id)); create table addresses (city_town varchar, address_id varchar, PRIMARY KEY (city_town)); create table performers (address_id varchar, PRIMARY KEY (address_id))
select t1.city_town from addresses as t1 join customers as t2 on t1.address_id = t2.address_id except select t1.city_town from addresses as t1 join performers as t2 on t1.address_id = t2.address_id