Query to Find maximum possible combinations between two columns - sql

Question

The target is to create all possible combinations of joining the two columns. every article of the first column ('100','101','102','103') must be in the combination result.
Sample Code
create table basis
(article Integer,
supplier VarChar(10) );
Insert into basis Values (100, 'A');
Insert into basis Values (101, 'A');
Insert into basis Values (101, 'B');
Insert into basis Values (101, 'C');
Insert into basis Values (102, 'D');
Insert into basis Values (103, 'B');
Result set
combination_nr;article;supplier
1;100;'A'
1;101;'A'
1;102;'D'
1;103;'B'
2;100;'A'
2;101;'B'
2;102;'D'
2;103;'B'
3;100;'A'
3;101;'C'
3;102;'D'
3;103;'B'
Let suppose if we add one more row against 102 as 'A' then our result set will be like this
Also according to the below-given calculations now we have 24 result sets
1;100;'A'
1;101;'A'
1;102;'A'
1;103;'B'
2;100;'A'
2;101;'A'
2;102;'D'
2;103;'B'
3;100;'A'
3;101;'B'
3;102;'A'
3;103;'B'
4;100;'A'
4;101;'B'
4;102;'D'
4;103;'B'
5;100;'A'
5;101;'C'
5;102;'A'
5;103;'B'
6;100;'A'
6;101;'C'
6;102;'D'
6;103;'B'
Already tried code
I have tried different Cross Joins but they always give exceeded rows according to my result sets.
SELECT article, supplier
FROM (SELECT DISTINCT supplier FROM basis2) AS t1
CROSS JOIN (SELECT DISTINCT article FROM basis2) AS t2;
Calculations:
article 100: 1 supplier ('A')
article 101: 3 suppliers ('A','B','C')
article 102: 1 supplier ('D')
article 103: 1 supplier ('B')
unique articles: 4 (100,101,102,103)
1x3x1x1 x 4 = 12 (combination rows)

Answer 1

You can do what you want using a recursive CTE. It is easier to put the combinations in single rows rather than across multiple rows:
with b as (
select b.*, dense_rank() over (order by article) as seqnum
from basis b
),
cte as (
select convert(varchar(max), concat(article, ':', supplier)) as suppliers, seqnum
from b
where seqnum = 1
union all
select concat(cte.suppliers, ',', concat(article, ':', supplier)), b.seqnum
from cte join
b
on b.seqnum = cte.seqnum + 1
)
select row_number() over (order by suppliers), suppliers
from (select cte.*, max(seqnum) over () as max_seqnum
from cte
) cte
where seqnum = max_seqnum;
For your particular result set, you can unroll the string:
with b as (
select b.*, dense_rank() over (order by article) as seqnum
from basis b
),
cte as (
select convert(varchar(max), concat(article, ':', supplier)) as suppliers, seqnum
from b
where seqnum = 1
union all
select concat(cte.suppliers, ',', concat(article, ':', supplier)), b.seqnum
from cte join
b
on b.seqnum = cte.seqnum + 1
)
select seqnum,
left(s.value, charindex(':', s.value) - 1) as article,
stuff(s.value, 1, charindex(s.value, ':'), '') as supplier
from (select row_number() over (order by suppliers) as seqnum, suppliers
from (select cte.*, max(seqnum) over () as max_seqnum
from cte
) cte
where seqnum = max_seqnum
) cte cross apply
string_split(suppliers, ',') s;
Here is a db<>fiddle.