CREATE TABLE "company" (
"Company_ID" int,
"Rank" int,
"Company" text,
"Headquarters" text,
"Main_Industry" text,
"Sales_billion" real,
"Profits_billion" real,
"Assets_billion" real,
"Market_Value" real,
PRIMARY KEY ("Company_ID")
)

CREATE TABLE "gas_station" (
"Station_ID" int,
"Open_Year" int,
"Location" text,
"Manager_Name" text,
"Vice_Manager_Name" text,
"Representative_Name" text,
PRIMARY KEY ("Station_ID")
)

CREATE TABLE "station_company" (
"Station_ID" int,
"Company_ID" int,
"Rank_of_the_Year" int,
PRIMARY KEY ("Station_ID","Company_ID"),
FOREIGN KEY (`Station_ID`) REFERENCES `gas_station`(`Station_ID`),
FOREIGN KEY (`Company_ID`) REFERENCES `company`(`Company_ID`)
)
SELECT DISTINCT main_industry FROM company
Show all main industry for all companies.