Oracle query eliminate duplicates not considering Null - sql

Question

I've performed a full outer join where I get the following:
ColumnFromTable1 ColumnFromTable2
AAA ABA
AAA Null <- remove
AAA ACC
BBB Null
CCC CDC
Null EFE
DDD FFF
Null FFF <- remove
GGG FFF
What I really want is to squash down the rows to remove duplicates such that my results would be:
ColumnFromTable1 ColumnFromTable2
AAA ABA
AAA ACC
BBB Null
CCC CDC
Null EFE
DDD FFF
GGG FFF
Basically I need to eliminate
AAA Null
Null FFF
since I have an AAA or FFF with a non-null. But I need to keep
BBB Null
Null EFE
because there is no BBB or EFE with a non-null
I've tried modifying my full outer join (which I can post if need be) and also tried wrapping these results in a sub query.
EDIT here is the query simplified for this post
select ColumnFromTable1, ColumnFromTable2 from Table1 t1
full outer join Table2 t2 on t1.common_code = t2.common_code
group by ColumnFromTable1, ColumnFromTable2

Answer 1

row_number() looks promising:
select c1, c2
from (
select c1, c2,
row_number() over (partition by c1 order by c2) r1,
row_number() over (partition by c2 order by c1) r2
from t)
where not ((c1 is null and r2 > 1) or (c2 is null and r1 > 1))
demo
It eliminates null values when they are not first in order.

Answer 2

Placing the full outer join you already computed in a CTE, you can filter it further as you want by doing:
with f (c1, c2) as (
... -- full outer join you already computed here
)
a (x) as ( -- repeated c1 with non-null c2
select c1
from f
group by c1
having count(c2) > 0
),
b (x) as ( -- repeated c2 with non-null c1
select c2
from f
group by c2
having count(c1) > 0
)
select *
from f
where not(c1 in (select x from a) and c2 is null)
and not(c2 in (select x from b) and c1 is null)