CREATE TABLE addresses (city VARCHAR2, address_id VARCHAR2)
CREATE TABLE people_addresses (address_id VARCHAR2)

Find distinct cities of addresses of people?
SELECT DISTINCT T1.city FROM addresses AS T1 JOIN people_addresses AS T2 ON T1.address_id = T2.address_id
SELECT DISTINCT "T1"."city" FROM "addresses" "T1" JOIN "people_addresses" "T2" ON "T1"."address_id" = "T2"."address_id"