JOIN and UPDATE

Question

I have two tables
Flight (FlightID, FlightDate, Origin, Destination, MaxCapacity, AvailableSeats)
FlightBooking(BookingID, CustomerID, FlightID, NumSeats, Status, BookingTime)
I'd like to somehow update AvailableSeats, given a change in Status.
When a FlightBooking is cancelled, the status is changed to 'C', then it is required to substract NumSeats from AvailableSeats (in flight), to simulate the cancellation and free up the seats associated with the cancelled booking.
A constraint is that only the BookingID is given (The rest of the data is already there, my java program just asks for the BookingID that needs to be cancelled). So somehow I need to join the two tables (via the only common column FlightID), and then update available seats.
Any ideas as to how this update and join could be combined would be much appreciated.

Answer 1

hi
I would sugget you to use database trigger yours front end just have to handle issue simple DML rest is to handle yours db trigger.
SQL>desc flight
Name                            Null?    Type
FLIGHTID                                 NUMBER
FLIGHTDATE                               DATE
ORIGIN                                   VARCHAR2(10)
DESTINATION                              VARCHAR2(10)
MAXCAPACITY                              NUMBER
AVAILABLESEATS                           NUMBER
SQL>desc flightbooking
Name                            Null?    Type
BOOKINGID                                NUMBER
CUSTOMERID                               VARCHAR2(10)
FLIGHTID                                 NUMBER
NUMSEATS                                 NUMBER
STATUS                                   VARCHAR2(1)
BOOKINGTIME                              DATE
SQL> insert into flight values (1,sysdate,'ROTERDAM','TOKYO',100,100);
1 row created.
SQL> commit;
Commit complete.
SQL> select * from flight;
FLIGHTID FLIGHTDAT ORIGIN     DESTINATIO MAXCAPACITY AVAILABLESEATS
        1 13-MAR-06 ROTERDAM   TOKYO              100             100
SQL> select * from flightbooking;
no rows selected
SQL> insert into flightbooking values (1,'0001',1,10,'B',sysdate);
1 row created.
SQL> commit;
Commit complete.
SQL> select * from flight;
FLIGHTID FLIGHTDAT ORIGIN     DESTINATIO MAXCAPACITY AVAILABLESEATS
        1 13-MAR-06 ROTERDAM   TOKYO              100             90
SQL> update flightbooking set numseats=20 where flightid=1;
1 row updated.
SQL> select * from flight;
FLIGHTID FLIGHTDAT ORIGIN     DESTINATIO MAXCAPACITY AVAILABLESEATS
        1 13-MAR-06 ROTERDAM   TOKYO              100             80
SQL> delete from flightbooking where flightid=1;
1 row deleted.
SQL> commit;
Commit complete.
SQL> select * from flight;[pre]
[pre] FLIGHTID FLIGHTDAT ORIGIN     DESTINATIO MAXCAPACITY AVAILABLESEATS
        1 13-MAR-06 ROTERDAM   TOKYO              100            100
SQL> insert into flightbooking values (1,'0001',1,10,'B',sysdate);
1 row created.
SQL> commit;
Commit complete.
SQL> select * from flight;
FLIGHTID FLIGHTDAT ORIGIN     DESTINATIO MAXCAPACITY AVAILABLESEATS
        1 13-MAR-06 ROTERDAM   TOKYO              100             90
SQL>  update flightbooking set status='C' where flightid=1;
1 row updated.
SQL> commit;
Commit complete.
SQL> select * from flight;
FLIGHTID FLIGHTDAT ORIGIN     DESTINATIO MAXCAPACITY AVAILABLESEATS
        1 13-MAR-06 ROTERDAM   TOKYO              100            100
SQL> update flightbooking set status='B' where flightid=1;
1 row updated.
SQL> select * from flight;
FLIGHTID FLIGHTDAT ORIGIN     DESTINATIO MAXCAPACITY AVAILABLESEATS
        1 13-MAR-06 ROTERDAM   TOKYO              100             90Khurram Siddiqui
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