CREATE TABLE employment (company_id NUMBER, people_id NUMBER, year_working NUMBER)
CREATE TABLE people (people_id NUMBER, age NUMBER, name CLOB, nationality CLOB, graduation_college CLOB)
CREATE TABLE company (company_id NUMBER, name CLOB, headquarters CLOB, industry CLOB, sales_in_billion NUMBER, profits_in_billion NUMBER, assets_in_billion NUMBER, market_value_in_billion NUMBER)

Show the headquarters that have at least two companies.
SELECT headquarters FROM company GROUP BY headquarters HAVING COUNT(*) >= 2
SELECT "headquarters" FROM "company" GROUP BY "headquarters" HAVING COUNT(*) >= 2