Simplest way to deal with multiple-row-pair

Question

Hi,
I have the following issue:
Here is the example data set:
Sender - Receiver - Volume
A B 50
B A 60
C D 70
B C 90
B D 80
I would like to report all the communicating pairs and if possible the volume communicated, getting rid of the logical duplicates (A->B = B->A in my case).
Result would be: A->B 110, C->D 70, B->C 90, B->D 80
Anyone has an idea on the simplest way to achieve this ?
Thanks for your help !

Answer 1

Rob,
I had a similar task which I solved by more complicated way.
I've reproduced it now using your way
May be interesting for somebody.
It is something lile this...
We have:
COL   VALU
A          1
B          2
C          4
D          3
E          1
We want to find all combination of col where sum of valu = 5
B                    D                       5                                     
C                    E                       5                                     
A                    C                       5                                     
DROP TABLE test_pairs
CREATE TABLE test_pairs (col1 VARCHAR2(1), valu NUMBER(2))
INSERT INTO test_pairs
     VALUES ('A', 1)
INSERT INTO test_pairs
     VALUES ('B', 2)
INSERT INTO test_pairs
     VALUES ('C', 4)
INSERT INTO test_pairs
     VALUES ('D', 3)
INSERT INTO test_pairs
     VALUES ('E', 1)
COMMIT
SELECT *
  FROM test_pairs;
SELECT DISTINCT LEAST (a.col1, b.col1), GREATEST (a.col1, b.col1),
                (a.valu + b.valu) sum_valu
           FROM test_pairs a, test_pairs b
          WHERE a.valu + b.valu = 5--I have used cartesian join to find all combinations and distinct remove duplicates for each pair.