How to do an INNER JOIN on multiple columns

Question

I\'m working on a homework project and I\'m supposed to perform a database query which finds flights either by the city name or the airport code, but the flights

Answer 1

You can JOIN with the same table more than once by giving the joined tables an alias, as in the following example:

SELECT 
    airline, flt_no, fairport, tairport, depart, arrive, fare
FROM 
    flights
INNER JOIN 
    airports from_port ON (from_port.code = flights.fairport)
INNER JOIN
    airports to_port ON (to_port.code = flights.tairport)
WHERE 
    from_port.code = '?' OR to_port.code = '?' OR airports.city='?'

Note that the to_port and from_port are aliases for the first and second copies of the airports table.