MySQL获得第一行值[关闭]

My whole query works apart from this sub query:

"(SELECT a.NumSeats From Aircrafts a WHERE f.AircraftID =a.AircrafID)"

I want that to return a number e.g 5

As I am selecting a.NumSeats which is an integer I can't understand why this doesn't work.

Also this query will return a MAX of 1 row.

$subQuery1 = "(SELECT COUNT(*) from Seats s WHERE s.FlightID = f.FlightID)";
    $subQuery2 = "(SELECT a.NumSeats From Aircrafts a WHERE f.AircraftID =a.AircrafID)";
    $subQuery2 = 0;
    $query = mysql_query("SELECT * FROM Flights f WHERE f.DeptAirport = '".$dep."' AND f.ArrAirport = '".$arr.
            "' AND f.Date=STR_TO_DATE('".$depDate."', '%Y-%m-%d') AND ".$subQuery1. "=" .$subQuery2);

If i remove $subQuery2 = 0 it breaks

I think a.AircrafID should be a.AircraftID.