Question

CREATE TABLE Flight 
(
    FlightID INTEGER NOT NULL,
    FlightDate TIMESTAMP NOT NULL, 
    Origin VARCHAR(30) NOT NULL,
    Destination VARCHAR(30) NOT NULL,
    MaxCapacity INTEGER NOT NULL,
    PricePerSeat DECIMAL NOT NULL

)
CREATE TABLE FlightBooking 
(
    BookingID INTEGER NOT NULL,
    CustomerID INTEGER NOT NULL,
    FlightID INTEGER NOT NULL, 
    NumSeats INTEGER NOT NULL,
    Status CHAR(1) NOT NULL,
    BookingTime TIMESTAMP NOT NULL,
    TotalCost DECIMAL

)
status = Reserve, Held Cancelled or Expired (only reserved and held are taken into account)
CREATE TABLE SeatBooking
(
    BookingID INTEGER NOT NULL,
    PassengerID INTEGER NOT NULL,
    SeatNumber CHAR(4) 

)

无论如何，如果给出了flightid，我可以获得座位的状态，以及可用座位总数，预留座位总数和总座位数

Answer 1

无论如何，如果flightid是，我可以得到座位的状态给定和总可用座位总数预留座位和总持有座位

是的！我假设使用Oracle，SQL Server或DB2并使用CTE。如果您没有其中一个，则必须使用子查询或临时表。

如果'R'是状态代码，则预留座位总数（如果您想在where子句中使用，则可以将此限制为单个航班，但这些查询会为您提供所有航班ID的值）：

SELECT SUM(NumSeats), FlightID
FROM FlightBooking 
WHERE Status = 'R'
GROUP BY FlightID

如果“H”是状态代码，则持有座位总数：

SELECT SUM(NumSeats), FlightID
FROM FlightBooking 
WHERE Status = 'H'
GROUP BY FlightID

总的可用座位是：

  WITH used AS
   (
      SELECT SUM(NumSeats) as used, FlightID
      FROM FlightBooking 
      WHERE Status in ('R','H')
      GROUP BY FlightID
   )
   SELECT F.MaxCapacity-U.Used, F.FlightID
   FROM used U
   JOIN Flight F ON U.FlightID = F.FlightID

Answer 2

根据航班ID，您应该能够获得总可用座位，预留座位总数和总座位数，如下所示：

select MaxCapacity - Reserved - Held as Available, Reserved, Held
from
(select f.MaxCapacity,
        sum(case b.status when 'R' then b.NumSeats end) Reserved,
        sum(case b.status when 'H' then b.NumSeats end) Held
 from Flight f
 left join FlightBooking b on f.FlightID = b.FlightID
 where f.FlightID = ?) sq

SQL，加入两个或多个表并返回结果

2 个答案: