Table: airlines_tunisia
Columns: airline
airline_in_arabic
icao
callsign
commenced_operations

Question: What is the ICAO with commenced operations before 1989?
SQL: SELECT "icao" FROM airlines_tunisia WHERE "commenced_operations" < 1989

Question: What is the lowest commenced operations that has a nouvelair callsign?
SQL: SELECT MIN("commenced_operations") FROM airlines_tunisia WHERE "callsign" = 'nouvelair'

Question: What callsign has commenced operations in 2011?
SQL: SELECT "callsign" FROM airlines_tunisia WHERE "commenced_operations" = 2011