title: LISTAGG, change sorting of result with reference to another column
body: <p>I have a table like this:</p>
  
  <pre><code>item   Desc
  ----   ----
  CSH    Cash
  CHQ    Cheque
  CDJ    Cross Department
  EPS    EPS
  </code></pre>
  
  <p>and I have SQL like this:</p>
  
  <pre><code>SELECT LISTAGG(a.item, ', ') WITHIN GROUP (ORDER BY a.item ASC) "item",
  LISTAGG(a.Desc, ', ') WITHIN GROUP (ORDER BY a.Desc ASC) "Desc"
  FROM tableA a;
  </code></pre>
  
  <p>and the result is like:</p>
  
  <pre><code>item                 Desc
  ----                 ----
  CDJ,CHQ,CSH,EPS      Cash,Cheque,Cross Department,EPS
  </code></pre>
  
  <p>however, my expected result is to sort 'item' according to the ordering of 'Desc', which means:</p>
  
  <p>'CSH,CHQ,CDJ,EPS'</p>
  
  <p>what can I do about it?</p>