Cartesian product to same table in oracle without duplicate

Question

I have a table and i want to produce a Cartesian of that data with same table itself.

TABLE:  TEMP_TEST

         FROM_COL   
        --------------
            A      
            B   
            C

If I write the below query for Cartesian then I get the output

     SELECT A.FROM_COL FROM_COL1,
  B.FROM_COL FROM_COL2
FROM TEMP_TEST A,
  TEMP_TEST B
WHERE A.FROM_COL!=B.FROM_COL ;

output

 FROM_COL1 FROM_COL2
    A              B
    A              C
    B              A
    B              C
    C              A
    C              B

But if A to B is present i don't want B to A. How I can I write a query for that?

I need the below output

FROM_COL1 FROM_COL2
        A              B
        A              C
        B              C

score 3 · Answer 1 · answered Aug 28 '15 at 16:18

You were very close. Just change your != into <:

with temp_test as (select 'A' from_col from dual union all
                   select 'B' from_col from dual union all
                   select 'C' from_col from dual)
select a.from_col from_col1,
       b.from_col from_col2
from   temp_test a,
       temp_test b
where  a.from_col < b.from_col;

FROM_COL1 FROM_COL2
--------- ---------
A         B        
A         C        
B         C

It would be better (ie. more readable/industry standard) if you rewrote the query using ANSI join syntax, though:

select a.from_col from_col1,
       b.from_col from_col2
from   temp_test a
       inner join temp_test b on (a.from_col < b.from_col);

Cartesian product to same table in oracle without duplicate

1 Answers1