Oracle 10g: parsing 2 columns merging duplicates

Question

I\'m having a table with 3 columns: DATE_A, DATE_B and ISSUE DATE_A and DATE_B can be filled in 3 possible ways:

Answer 1

If I understand correctly, you want a union all of the date values and string aggregation. listagg() was introduced in 11g, but you can use wm_concat():

select dte, wm_concat(issue) as issues
from ((select date_a as dte, issue from t where date_a is not null) union all
      (select date_b, issue from t where date_b is not null)
     ) di
group by dte
order by dte;