CREATE TABLE company (company VARCHAR, main_industry VARCHAR, company_id VARCHAR)
CREATE TABLE station_company (company VARCHAR, main_industry VARCHAR, company_id VARCHAR)

Show company name and main industry without a gas station.
SELECT company, main_industry FROM company WHERE NOT company_id IN (SELECT company_id FROM station_company)
SELECT "company", "main_industry" FROM "company" WHERE NOT "company_id" IN (SELECT "company_id" FROM "station_company")