Can STUFF function return NULL values?
<p>I'm looking at the following link:</p>

<p><a href="https://stackoverflow.com/questions/2046037/can-i-comma-delimit-multiple-rows-into-one-column?noredirect=1&amp;lq=1">Can I Comma Delimit Multiple Rows Into One Column?</a></p>

<p>The query used in the solution is exactly what I need, but also need to return NULL values.</p>

<pre><code>SELECT t.TicketID,
   STUFF(ISNULL((SELECT ', ' + x.Person
            FROM @Tickets x
           WHERE x.TicketID = t.TicketID
        GROUP BY x.Person
         FOR XML PATH (''), TYPE).value('.','VARCHAR(max)'), ''), 1, 2, '') [No Preceeding Comma]
FROM @Tickets t
GROUP BY t.TicketID
</code></pre>

<p>This works great if each [TicketID] has an associated [Person].  </p>

<p>But if the Person is NULL, for the TicketID, I need to return just the TicketID and have the Person show as NULL or blank. I'm having trouble removing the ISNULL cleanly.</p>

<p>From this:</p>

<pre><code>[TicketID], [Person]
 T0001       Alice
 T0001       Bob
 T0002       Catherine
 T0002       Doug
 T0003       Elaine
 T0004       NULL
</code></pre>

<p>To this:</p>

<pre><code>[TicketID], [Person]
 T0001       Alice, Bob
 T0002       Catherine, Doug
 T0003       Elaine
 T0004       NULL
</code></pre>