Question

我的第一个查询返回值20：

    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'
     )

我的第二个查询返回1：

    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

现在我的问题是我想从第二个查询中减去第一个查询并给我答案19.我该怎么做？

Answer 1

您可以使用sub sql来减去

SELECT numberofseats - ( 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)
    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'
     )

Answer 2

你可以通过以下方式完成：

SELECT (query1) - (query2)

或

SELECT (query1)  - (query2) AS Difference

或

select @result = (query1) - (query2)

如何在sql中减去两个查询？

2 个答案: