Puedes usar listagg() función analítica de ventana dos veces como
with t1( Base, End ) as
(
select 'RMSA','Item 1' from dual union all
select 'RMSA','Item 2' from dual union all
select 'RMSA','Item 3' from dual union all
select 'RMSB','Item 1' from dual union all
select 'RMSB','Item 2' from dual union all
select 'RMSC','Item 4' from dual
),
t2 as
(
select
listagg(base,';') within group (order by end)
as key,
end
from t1
group by end
)
select key,
listagg(end,',') within group (order by end)
as Products
from t2
group by key
order by products;
Key Products
--------- --------------
RMSA;RMSB Item 1, Item 2
RMSA Item 3
RMSC Item 4
