3 Way join with different column names.

I believe what you are looking for is a query like this:

select f3.deptname dept_name, sum(isnull(f2.salary,0)) amt_spent_each_dept
from file3 f3 left join file1 f1 on (f3.deptid = f1.deptid)
left join file2 f2 on (f1.empid = f2.empid)
group by f3.deptname
order by f3.deptname

Thanks for the reply...but i want to do this in ab initio .....could you be a bit more specific... i will explain the question again..

Code
Hi,
 
I have 3 files  each having 2 cols
e.g
File1
empid       deptid
1                 100   
2                 200
3                 200
4                 100
5                 300
 
File2
empid       salary
1                 10  
2                  20
3                  30
4                  40
5                  50
6                  60
 
File3
deptid      deptname
100           A
200           B
300           C
400           D
 
in the output i want total amt spent on each dept i.e A,B,C,D which would be a sum in rollup for each dept(100,200,300,400) salary of each employee.
 
So here i will have to join 
File1.empid =File2.empid  (which gives salaries) AND
File1.deptid = File3.deptid (which gives dept name)
 
So... in o/p i want dept_name and amt_spent_each_dept
 
My solution has 
File1 ---
File2   ------[ JOIN] ---[Rollup] --- [File4 as output]
File3 ---
 
But what condition can i have in JOIN component to join these 3 tables ?
 

Setup the join component- Fine .. I will answer this myself You don't need to mention a key here ..neither key nor override key So in the transform you have find the columns u need to match and put a condition for them in each column. so u may get a cartesian product and after that check it with a filter by expression where you don't need null (check this with is_valid or is_null) and then fwd it to sort where key is dept_id and then to roll up where key is again dept_id and roll up on sal So here you get your result for each dept expense.

Code
  SELECT C.DEPTNAME,sum(B.SALARY) FROM FILE1 A ,FILE2 B ,FILE3 C
  WHERE A.EMPLID=B.EMPLID AND A.DEPTID=C.DEPTID
  GROUP BY C.DEPTNAME

Step 1: File1 - left outer Join {Key- empid} with -File2

Step 2: The above output flow should be sort{PBKS-if multifile} based on key empid

Step 3: The step 2s o/p flow to be left outer join {key: deptid} with -File 3

Step 4: In Rolloup-sum the the salary and map it to total_amt based on key deptid.

Step 5: FIle 4 will be ready now with required o/p (deptid,dept_name & total_amt)