CREATE TABLE "airlines_based_in_changi" (
  "airline" text,
  "iata" text,
  "icao" text,
  "callsign" text,
  "commenced_operations" real
);

Question: Which Callsign has an IATA of tr?
SQL: SELECT "callsign" FROM "airlines_based_in_changi" WHERE "iata"='tr';

Question: Which Commenced operations have an Airline of valuair?
SQL: SELECT "commenced_operations" FROM "airlines_based_in_changi" WHERE "airline"='valuair';

Question: Which Commenced operations have an Airline of valuair?
SQL: SELECT MAX("commenced_operations") FROM "airlines_based_in_changi" WHERE "airline"='valuair';

Question: Which IATA has a ICAO of slk?
SQL: SELECT "iata" FROM "airlines_based_in_changi" WHERE "icao"='slk';