Question

I have one table like this (report)

--------------------------------------------------
|  user_id |  Department | Position  | Record_id |
--------------------------------------------------
|  1       |  Science    | Professor |  1001     |
|  1       |  Maths      |           |  1002     |
|  1       |  History    | Teacher   |  1003     |
|  2       |  Science    | Professor |  1004     |
|  2       |  Chemistry  | Assistant |  1005     |
--------------------------------------------------

I’d like to have the following result

   ---------------------------------------------------------
   | user_id  |  Department+Position                       |
   ---------------------------------------------------------
   |  1       | Science,Professor;Maths, ; History,Teacher |
   |  2       | Science, Professor; Chemistry, Assistant   |
   ---------------------------------------------------------

That means I need to preserve the empty space as ‘ ‘ as you can see in the result table.
Now I know how to use LISTAGG function but only for one column. However, I can’t exactly figure out how can I do for two columns at the sametime. Here is my query:

SELECT user_id, LISTAGG(department, ';') WITHIN GROUP (ORDER BY record_id)
FROM report

Thanks in advance 🙂

Answer 1

It just requires judicious use of concatenation within the aggregation:

select user_id
     , listagg(department || ',' || coalesce(position, ' '), '; ')
        within group ( order by record_id )
  from report
 group by user_id

i.e. aggregate the concatentation of department with a comma and position and replace position with a space if it is NULL.