Please help :( finding the diference between a table value and a count

Question

Ok... Pretty much, atm I am trying to make a view which is a capacity (specified by a table) minus a count(*) of all the tables, what I am doing is getting the capacity and atempting to take it away from a joined table which contains all of the people booked into a certain flight.. I know it sounds crazy, but I'm sure (surely hopeful) it will work..
To sum my question up, how can I make a view which has one table minus a numerical result from a count(*)... If I can that is.
EDIT:
I have made somthing which could be possibly ported into a function which returns the correct answer.. maybe is it better/possible to make the view somehow start a function?
Edited by: 893357 on Oct 26, 2011 11:17 AM

Answer 1

How about starting with this "design" (I came up with it in 20minutes so it can be refined further)
FLIGHT_MASTER
(FLIGHT_NUMBER  VARCHAR2(6) primary key,
FROM_CITY_CD  VARCHAR2(6),
TO_CITY_CD    VARCHAR2(6)
FLIGHT_DETAILS
(FLIGHT_ID     NUMBER primary key,
FLIGHT_NUMBER VARCHAR2(6) foreign key references FLIGHT_MASTER (FLIGHT_NUMBER),
SCHEDULED_DEPARTURE DATE,
ACTUAL_DEPARTURE DATE,
TOTAL_SEATS NUMBER(4,0),
BOOKED_SEATS NUMBER(4,0)
FLIGHT_BOOKINGS
(PNR          VARCHAR2(6) primary key,
FLIGHT_ID    NUMBER foreign key references FLIGHT_DETAILS (FLIGHT_ID),
SEATS_BOOKED NUMBER(4,0)
PASSENGER_DETAILS
(PASSSENGER_ID  NUMBER primary key,
PNR          VARCHAR2(6) foreign key references FLIGHT_BOOKINGS (PNR),
TICKET_TYPE_FLAG  VARCHAR2(3),
PASSENGER_FIRST_NAME VARCHAR2(30),
PASSENGER_SECOND_NAME VARCHAR2(30),
PASSENGER_LAST_NAME  VARCHAR2(30),
PASSENGER_PHONE    VARCHAR2(30),
PASSENGER_ADDRESS_1  VARCHAR2(60),
PASSENGER_ADDRESS_2  VARCHAR2(60),
PASSENGER_ADDRESS_3  VARCHAR2(60),
PASSENGER_CITY       VARCHAR2(60),
PASSENGER_COUNTRY    VARCHAR2(60)
select fm.flight_number, fm.from_city, fd.flight_id, fd.scheduled_departure, fd.total_seats,
fd.total_seats - fd.booked_seats available_seats
from flight_master fm, flight_details fd
where fm.flight_number='&flight'
and fd.scheduled_departure = '&scheduled_date_time'
and fm.flight_number=fd.flight_number
-- whenever a new reservation is made (only if available_seats >= required_seats)
select from flight_details for update of booked_seats where .....
insert into flight_bookings ...
insert into passenger_details ...
... store the number of seats in a variable :purchased_seats
update flight_details set booked_seats = booked_seats + :purchased_seats
commitHemant K Chitale