Show the name of the company with company id 1?
select company from company where company_id = '1'
Show all company name and main industry with gas station?
select company, main_industry from company where company_id in ( select company_id from station_company )
Show all company name and main industry without a gas station?
select company, main_industry from company where company_id not in ( select company_id from station_company )