title: LISTAGG function with two columns
body: <p>I have one table like this (report)</p>
  
  <pre><code>--------------------------------------------------
  |  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     |
  --------------------------------------------------
  </code></pre>
  
  <p>I'd like to have the following result</p>
  
  <pre><code>   ---------------------------------------------------------
     | user_id  |  Department+Position                       |
     ---------------------------------------------------------
     |  1       | Science,Professor;Maths, ; History,Teacher |
     |  2       | Science, Professor; Chemistry, Assistant   |
     ---------------------------------------------------------
  </code></pre>
  
  <p>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:</p>
  
  <pre><code>SELECT user_id, LISTAGG(department, ';') WITHIN GROUP (ORDER BY record_id)
  FROM report
  </code></pre>
  
  <p>Thanks in advance :-)</p>