Oracle pl/sql permutation and combination - sql

Question

I am not sure what is the correct search term for this, please let me know if there's already an answer for this.
eg:
I have these data
A
B
C
D
E
What is the best way to calculate the addition of each possible combination? Such as:
A
A+B
A+C
A+D
A+E
A+B+C
A+B+D
A+B+E
A+C+D
A+C+E
A+C+D+E
A+B+C+D
A+B+C+E
A+B+C+D+E
B
B+C
B+D
B+E
B+C+D
B+C+E
B+C+D+E
C
C+D
C+E
...
The list goes on.......
Is there any way to achieve this?
The 5 data are not fixed. I might have 10.. 20 or 50 or 1000 :(
Thank you.

Answer 1

In SQL, you can almost do this with this set of left joins:
select (t1.col + coalesce(t2.col, 0) + coalesce(t3.col, 0) +
coalesce(t4.col, 0) + coalesce(t5.col, 0)
) as sumcombo
from t t1 left join
t t2
on t1.col < t2.col left join
t t3
on t2.col < t3.col left join
t t4
on t3.col < t4.col left join
t t5
on t4.col < t5.col;
It doesn't quite work, because you can never get just "A" for instance. Instead:
with t as (
select col
from table
union all
select NULL
from dual
)
select (t1.col + coalesce(t2.col, 0) + coalesce(t3.col, 0) +
coalesce(t4.col, 0) + coalesce(t5.col, 0)
) as sumcombo
from table t1 left join
t t2
on t1.col < t2.col or t2.col is null left join
t t3
on t2.col < t3.col or t3.col is null left join
t t4
on t3.col < t4.col or t4.col is null left join
t t5
on t4.col < t5.col or t5.col is null;

Answer 2

This can be solved by a hierarchical query. First of all, build a further child column col2 for connection:
-- your test data set
with testdata as
(select 'A' as col from dual
union
select 'B' from dual
union
select 'C' from dual
union
select 'D' from dual
union
select 'E' from dual),
-- create child column
testdata2 as
(select t.col as col1, t.col as col2 from testdata t)
select level, sys_connect_by_path(col1, '/') path
from testdata2 t
connect by prior col1 < col2
order by level, sys_connect_by_path(col1, '/');
result:
1 /A
1 /B
1 /C
1 /D
1 /E
2 /A/B
2 /A/C
2 /A/D
2 /A/E
2 /B/C
2 /B/D
2 /B/E
2 /C/D
2 /C/E
2 /D/E
3 /A/B/C
3 /A/B/D
3 /A/B/E
3 /A/C/D
3 /A/C/E
3 /A/D/E
3 /B/C/D
3 /B/C/E
3 /B/D/E
3 /C/D/E
4 /A/B/C/D
4 /A/B/C/E
4 /A/B/D/E
4 /A/C/D/E
4 /B/C/D/E
5 /A/B/C/D/E