Select everything and distinct

[NZ_Kiwis]

$result = mysql_query ("SELECT DISTINCT thread_id FROM forum_posts ORDER BY id DESC LIMIT 20");

This gets 20 dustinct rows.... how can I get other data from these rows?

Almost like

$result = mysql_query ("SELECT DISTINCT thread_id, id FROM forum_posts ORDER BY id DESC LIMIT 20");

But this does not work.

[cahva]

Group by?

SELECT thread_id, id FROM forum_posts GROUP BY thread_id ORDER BY id DESC LIMIT 20