For Each Combination of Two Cols Create a Record

Question

How do I PL/SQL creating a new record in table B for each combination of two columns in table A? Do I need to create a cursor?
my_cursor IS
SELECT col1, col2 FROM tableA
and then with a FOR loop somehow write SELECT FROM INSERT INTO?
Thanks,

Answer 1

For unique combination you have to do more than just distinct:
SQL> ed
Wrote file afiedt.buf
  1  select distinct least(x.id1, y.id2) as num1, greatest(x.id1, y.id2) as num2
  2  from t x, t y
  3* order by 1
SQL> /
      NUM1       NUM2
         1          2
         1          3
         1          4
         2          2
         2          3
         2          4
         3          3
         3          4
8 rows selected.
SQL>Which, as you can see strips out the 3,2 because we already have a 2,3
We have to use the greatest and least functions here so that the 3,2 combination was turned around to become 2,3 thus causing a duplicate which was stipped out using the distinct. There are other techniques too, but it depends on your data and what you want to achieve.