hello i am trying to find the sum of one column from table A and subtract it from a value of table B...how this can be done

b.value_x - SUM(a.column_y)

or

b.value_x - ( SUM(a.column_y) OVER(PARTITION BY ... ) )

depending on your requirement(sum over what group?).

actualy i'm a beginer in DB2 and i dont know how to compare those statements my actual problem is a booking flights annd im trying to find out the available seats in the table flights i have FlightID , FlightDate, Origin,Destination, MaxCapacity and in the other table te table flightbooking i have BookingID,CustomerID,FlightID,NumSeats,Status and BookingTime and i have to sum the numseats and subtruct from the max capacity.

But i cant find how to do the equation with alla the select statments... i mean to select...from...
select...from... where Flight.FLIGHTID = Flightbooking.Flightid
...and then i dont know how to complete that...can you help me??

Here is an example.

thanks very match is working=D

can i ask you something more??
------------------------------ Commands Entered ------------------------------
SELECT DISTINCT
flightBooking.FlightID,
Customer.CustomerID,
Customer.NAME
FROM
Customer
LEFT OUTER JOIN
flightbooking
ON flightbooking.flightid = 100;
------------------------------------------------------------------------------
SELECT DISTINCT flightBooking.FlightID, Customer.CustomerID, Customer.NAME FROM Customer LEFT OUTER JOIN flightbooking ON flightbooking.flightid = 100

FLIGHTID CUSTOMERID NAME
----------- ----------- --------------------
100 1 Andrew Brown
100 2 Andriani Papakwsta
100 3 Pra3ulla Theodoulou

3 record(s) selected.



here i'm trying to generate a list with the customer who are going to travel in a specific flight (100) but the result is a list with all the customers

i tried and..... ON flightbooking.status = 'r';
which mean that they are Reserved but i have the same problem

can you help me?

Why are you using outer join?

because i'm using the flightid the customerid and the customer name

OK then, do you know the difference between inner and outer joins? If not, I suggest you find some SQL guide for beginners and read it before you ruin your employer's reputation.

that helps a lot thanks