[filburt1]

It doesn't; only way I know if is to run that query to get the threadid, and then:
[sql]
SELECT pagetext, userid, username FROM post WHERE threadid = threadid ORDER BY dateline
[/sql]
Or, if you're running MySQL 4.1 which IIRC supports subselects:
[sql]
SELECT pagetext, userid, username FROM post WHERE threadid = (SELECT title, threadid FROM thread
WHERE forumid = forumid ORDER BY dateline DESC LIMIT 1) ORDET BY dateline[/sql]