Frequency of all combinations of values for certain column - sql

Question

I have a dataset in SQL Server 2012 with a column for id and value, like this:
[id] [value]
--------------
A 15
A 11
A 11
B 13
B 15
B 12
C 12
C 13
D 13
D 12
My goal is to get a frequency count of all combinations of [value], with two caveats:
Order doesn't matter, so [11,12,15] is not counted separately from [12,11,15]
Repeated values are counted separately, so [11,11,12,15] is counted separately from [11,12,15]
I'm interested in all combinations, of any length (not just pairs)
So the outcome would look like:
[combo] [frequency]
---------------------
11,11,15 1
12,13,15 1
12,13 2
I've seen answers here involving recursion that answer similar questions but where order counts, and answers here involving self-joins that yield pair-wise combinations. These come close but I'm not quite sure how to adapt for my specific needs.

Answer 1

You can use string_agg():
select vals, count(*) as frequency
from (select string_agg(value, ',') within group (order by value) as vals, id
from t
group by id
) i
group by vals;
SQL Server 2012 doesn't support string_agg() but you can use the XML hack:
select vals, count(*) as frequency
from (select id,
stuff( (select concat(',', value)
from t t2
where t2.id = i.id
for xml path ('')
), 1, 1, ''
) as vals
from (select distinct id from t) i
) i
group by vals;

Answer 2

Your number string is just all the values with the same id in increasing order. So I'm treating the lowest id as a canonical name for the full sequence and all its matches. This spares all the string manipulations though you can expand as necessary.
Just tag each duplicate value with a counter and then look for groups that pair up completely.
with data as (
select id, value,
row_number() over (partition by id, value) as rn
), matches as (
select l.id, r.id as match
from data l full outer join data r on
l.value = r.value and l.rn = r.rn and l.id <= r.id
group by l.id
having count(l.id) = count(*) and count(r.id) = count(*)
)
select id, count(match) as frequency
from matches
group by id;
The logic in the middle query is also easily adaptable for finding subset of values in common.

Answer 3

You can achieve this using CTEs and row_number functions.
DECLARE #table table(id CHAR(1), val int)
insert into #table VALUES
('A',15),
('A',11),
('A',11),
('B',13),
('B',15),
('B',12),
('C',12),
('C',13),
('D',13),
('D',12);
;WITH CTE_rnk as
(
SELECT id,val, row_number() over (partition by id order by val) as rnk
from #table
),
CTE_concat as
(
SELECT id, cast(val as varchar(100)) as val, rnk
from CTE_rnk
where rnk =1
union all
SELECT r.id, cast(concat(c.val,',',r.val) as varchar(100)) as val,r.rnk
from CTE_rnk as r
inner join CTE_concat as c
on r.rnk = c.rnk+1
and r.id = c.id
),
CTE_maxcombo as
(
SELECT id,val, row_number() over(partition by id order by rnk desc) as rnk
from CTE_concat
)
select val as combo, count(*) as frequency
from CTE_maxcombo where rnk = 1
group by val
+----------+-----------+
| combo | frequency |
+----------+-----------+
| 11,11,15 | 1 |
| 12,13 | 2 |
| 12,13,15 | 1 |
+----------+-----------+