SQL unique combinations - sql

Question

I have a table with three columns with an ID, a therapeutic class, and then a generic name. A therapeutic class can be mapped to multiple generic names.
ID therapeutic_class generic_name
1 YG4 insulin
1 CJ6 maleate
1 MG9 glargine
2 C4C diaoxy
2 KR3 supplies
3 YG4 insuilin
3 CJ6 maleate
3 MG9 glargine
I need to first look at the individual combinations of therapeutic class and generic name and then want to count how many patients have the same combination. I want my output to have three columns: one being the combo of generic names, the combo of therapeutic classes and the count of the number of patients with the combination like this:
Count Combination_generic combination_therapeutic
2 insulin, maleate, glargine YG4, CJ6, MG9
1 supplies, diaoxy C4C, KR3

Answer 1

One way to match patients by the sets of pairs (therapeutic_class, generic_name) is to create the comma-separated strings in your desired output, and to group by them and count. To do this right, you need a way to identify the pairs. See my Comment under the original question and my Comments to Gordon's Answer to understand some of the issues.
I do this identification in some preliminary work in the solution below. As I mentioned in my Comment, it would be better if the pairs and unique ID's existed already in your data model; I create them on the fly.
Important note: This assumes the comma-separated lists don't become too long. If you exceed 4000 characters (or approx. 32000 characters in Oracle 12, with certain options turned on), you CAN aggregate the strings into CLOBs, but you CAN'T GROUP BY CLOBs (in general, not just in this case), so this approach will fail. A more robust approach is to match the sets of pairs, not some aggregation of them. The solution is more complicated, I will not cover it unless it is needed in your problem.
with
-- Begin simulated data (not part of the solution)
test_data ( id, therapeutic_class, generic_name ) as (
select 1, 'GY6', 'insulin' from dual union all
select 1, 'MH4', 'maleate' from dual union all
select 1, 'KJ*', 'glargine' from dual union all
select 2, 'GY6', 'supplies' from dual union all
select 2, 'C4C', 'diaoxy' from dual union all
select 3, 'GY6', 'insulin' from dual union all
select 3, 'MH4', 'maleate' from dual union all
select 3, 'KJ*', 'glargine' from dual
),
-- End of simulated data (for testing purposes only).
-- SQL query solution continues BELOW THIS LINE
valid_pairs ( pair_id, therapeutic_class, generic_name ) as (
select rownum, therapeutic_class, generic_name
from (
select distinct therapeutic_class, generic_name
from test_data
)
),
first_agg ( id, tc_list, gn_list ) as (
select t.id,
listagg(p.therapeutic_class, ',') within group (order by p.pair_id),
listagg(p.generic_name , ',') within group (order by p.pair_id)
from test_data t join valid_pairs p
on t.therapeutic_class = p.therapeutic_class
and t.generic_name = p.generic_name
group by t.id
)
select count(*) as cnt, tc_list, gn_list
from first_agg
group by tc_list, gn_list
;
Output:
CNT TC_LIST GN_LIST
--- ------------------ ------------------------------
1 GY6,C4C supplies,diaoxy
2 GY6,KJ*,MH4 insulin,glargine,maleate

Answer 2

You are looking for listagg() and then another aggregation. I think:
select therapeutics, generics, count(*)
from (select id, listagg(therapeutic_class, ', ') within group (order by therapeutic_class) as therapeutics,
listagg(generic_name, ', ') within group (order by generic_name) as generics
from t
group by id
) t
group by therapeutics, generics;