Drew thank you very much for your help. Really apreciated. I just had to test all the possible data scenarios. My real table has more than 160 million records. However...

my apologies for the name confusion J. Drew.

I will check that part Jeff. I was checking all the possible scenarios and I think the query does not work for the following set of data:
create table VALUATION...

Awesome Jeff!!.  Thanks a lot. I think the following query is also rdbms agnostic:
with newtab (col1,col2, mtm)
as
(SELECT upper(col1), upper(col2), mtm FROM sampledata
  WHERE upper(col1) <...

Really sorry but business keep changing the requirements. My table is:
create table SampleData ( col1 VARCHAR(10), col2 VARCHAR(10), MTM numeric(10));
INSERT INTO SampleData VALUES
('A','B',100),
('B','A',-50),
('A','C',200),
('A','D',100),
('A','B',150),

unfortunately taht query did not encompass all scenarios such as:
col1 col2 col3
('A','B',100),
('B','A',-50),
('A','C',200),
('A','D',100),
('A','B',150),
('B','F',200),
('d','K',400),
('K','D',-20),
('C','D',-50),
('D','C',-60);
I need to display which one of...

Following query produced the expected results:
A    B    300
A    C    200
A    D    100
B    F    200
D    C    50

SELECT CASE WHEN COL1 <= COL2 AND COL3 > 0 THEN COL1 ELSE COL2 END AS COL1,
 CASE...

Sorry . that was only half of the work I had to do. tuens out that every time I have negative value in col3 I have to turn col3 positive...

That is excellent guys. Both queries work as expected. I have modified the query a little bit to accomodate a case when col3 is negative. In that case it means...

col1 and col2 represent company names and col3 is the transaction value, could be negative, between the companies. So I want to know how much company A spent?