-- Database schema
| company : Company_ID [ INT ] primary_key , Rank [ INT ] , Company [ TEXT ] , Headquarters [ TEXT ] , Main_Industry [ TEXT ] , Sales_billion [ INT ] , Profits_billion [ INT ] , Assets_billion [ INT ] , Market_Value [ INT ] | gas_station : Station_ID [ INT ] primary_key , Open_Year [ INT ] , Location [ TEXT ] , Manager_Name [ TEXT ] , Vice_Manager_Name [ TEXT ] , Representative_Name [ TEXT ] | station_company : Station_ID [ INT ] primary_key station_company.Station_ID = gas_station.Station_ID , Company_ID [ INT ] station_company.Company_ID = company.Company_ID , Rank_of_the_Year [ INT ] |
-- -- What are the different main industries for all companies?

SELECT DISTINCT main_industry FROM company;