title: How can I subtract two queries in sql?
body: <p>my first query returns me the value 20:</p>
  
  <pre><code>    SELECT numberofseats
      from plane
      where tail number in
       ( select flighttailnumberfk
         from flight
         where departuretime between '11/29/2014' and '11/30/2014' and
               flightdepartureairportfk = 'jfk' and
               flightarrivalairport = 'mli'
       )
  </code></pre>
  
  <p>and my second query returns me 1:</p>
  
  <pre><code>    select count(reservationseatfk)
      from flight f, reservation r
      where f.departuretime between '11/29/2014' and '11/30/2014' and
            f.reservationflightidfk = f.flightid and r.reservationdeparturetimefk = f.departuretime
  </code></pre>
  
  <p>Now my problem is that I want to subtract the first query from the second query and give me the answer 19. how do i do that?</p>