cartesian product

Hi,

I have a query regarding an SQL statement I'm trying to execute. I
have the following table:

sequence
-------------+
AK
AKCMK
CMKA

I execute the following statement (Cartesian product):

SELECT p1.sequence as sequence1, p2.sequence as sequence2
FROM potential_pairs p1, potential_pairs p2

which gives me:

sequence1 | sequence2
----------------+--------------AK           | AK AK           | AKCMK AK           | CMKA AKCMK    | AK AKCMK    |
AKCMKAKCMK    | CMKA CMKA      | AK CMKA      | AKCMK CMKA      | CMKA
 
(9 rows)

I want to eliminate duplicates and by duplicate I mean a tuple such as
{AK, CMKA} should be regarded as the same as {CMKA, AK}. So I would
like the following result:

sequence1 | sequence2
----------------+--------------AK           | AK AK           | AKCMK AK           | CMKA AKCMK    | AKCMK AKCMK    |
CMKACMKA      | CMKA
 

Any help would be appreciated.

- Salman