how to make into an array and also count - oracle

Question

I have this data:
app
asscs
mod_asscs
a
56
cb-56
a
67
cb-67
b
38
cb-38
a
12
12
I want to group by column 'app' and count the cases where 'mod_asscs' value is equal to concat('cb-', asscs). I also want to output the array in a separate column 'mod_asscs_array' so that the output is the following:
app
mod_asscs_array
scs_count
a
cb-56, cb-67
2
b
cb-38
1
So far this is what I have:
SELECT DISTINCT
app,
( CASE WHEN concat('cb-', asscs) = mod_asscs THEN mod_asscs || ',') AS mod_asscs_array,
COUNT( CASE WHEN concat('cb-', asscs) = mod_asscs THEN mod_asscs || ',') AS scs_count
FROM data_table
GROUP BY
app

Answer 1

Looks like aggregation.
Sample data:
SQL> with test (app, asscs, mod_asscs) as
2 (select 'a', 56, 'cb-56' from dual union all
3 select 'a', 67, 'cb-67' from dual union all
4 select 'b', 38, 'cb-38' from dual union all
5 select 'a', 12, '12' from dual
6 )
Query:
7 select app,
8 listagg(mod_asscs, ', ') within group (order by mod_asscs) array,
9 count(*) cnt
10 from test
11 where mod_asscs = 'cb-'|| asscs
12 group by app;
A ARRAY CNT
- -------------------- ----------
a cb-56, cb-67 2
b cb-38 1
SQL>

Answer 2

If you need to show all the "apps", even those with a "count" of zero, then you need conditional aggregation, something like this:
with
test (app, asscs, mod_asscs) as (
select 'a', 56, 'cb-56' from dual union all
select 'a', 67, 'cb-67' from dual union all
select 'b', 38, 'cb-38' from dual union all
select 'a', 12, '12' from dual union all
select 'c', 33, 'cb-23' from dual
)
select app,
listagg(case when mod_asscs = 'cb-' || asscs
then mod_asscs end, ', ')
within group (order by asscs) as mod_asscs_array,
count(case when mod_asscs = 'cb-' || asscs
then mod_asscs end) as scs_count
from test
group by app
order by app -- if needed
;
APP MOD_ASSCS_ARRAY SCS_COUNT
--- -------------------- ----------
a cb-56, cb-67 2
b cb-38 1
c 0

Answer 3

if there are duplicates in the array, do I do listagg(distinct.. and count(distinct case when ...?
You cannot use LISTAGG(DISTINCT ... as the LISTAGG function does not currently support the DISTINCT keyword; instead you need to use DISTINCT first in a sub-query and then use LISTAGG:
SELECT app,
LISTAGG(mod_asscs, ',') WITHIN GROUP (ORDER BY mod_asscs)
AS mod_asscs_array,
COUNT(*) AS scs_count
FROM (
SELECT DISTINCT
app,
mod_asscs
FROM data_table
WHERE 'cb-' || asscs = mod_asscs
)
GROUP BY app
Which, for the sample data:
CREATE TABLE data_table (app, asscs, mod_asscs) AS
SELECT 'a', 56, 'cb-56' FROM DUAL UNION ALL
SELECT 'a', 56, 'cb-56' FROM DUAL UNION ALL
SELECT 'a', 67, 'cb-67' FROM DUAL UNION ALL
SELECT 'b', 38, 'cb-38' FROM DUAL UNION ALL
SELECT 'a', 12, '12' FROM DUAL;
Outputs:
APP
MOD_ASSCS_ARRAY
SCS_COUNT
a
cb-56,cb-67
2
b
cb-38
1
db<>fiddle here