2 update for 2 table

[zodehala]

this is post table
[IMG]http://www.divran.com/script/upload/images/post.jpg[/IMG]

this is thread table
[IMG]http://www.divran.com/script/upload/images/thread.jpg[/IMG]

lie you see

firstpostid in thread table = postid in post table and threadid's

i wanna update title column in thread table as title in post table
but how ?

i create following query for trying but i t does not run

UPDATE 	thread
INNER 	JOIN post ON thread.threadid=post.threadid
SET 	thread.title=REPLACE(post.title)
WHERE 	post.postid=thread.firstpostid