Hi there. I'm in need of assistance with an update query. I am doing
a data migration for a message board. All went fine except some of
the mappings didn't cross over. Here is what I need to do:

Tables:
Thread: threadid, firstpostid, lastpostid
Post: postid, threadid, dateline

I need to map the first post from post.postid to thread.firstpostid
and the last post from post.postid to thread.lastpost id.

I can get these values by two queries if I know the threadid

First Post = select postid, threadid from post where post.threadid =
1 order by FROM_UNIXTIME(dateline) asc limit 1

Last Post = select postid, threadid from post where post.threadid = 1
order by FROM_UNIXTIME(dateline) desc limit 1

Does anyone know how I can seamlesly update the Thread table with
these post id's respectively through one subquery?

I am using MySQL 5.x

Thanks in advance

I'm not sure that MySQL 5.x accepts those sub-queries.

SELECT p1.threadid, p1.postid as firstpostid, p2.postid as lastpostid
FROM Post p1
, Post p2
WHERE FROM_UNIXTIME(p1.dateline)
= (SELECT MIN(FROM_UNIXTIME(dateline))
FROM Post
WHERE threadid = 1
)
AND FROM_UNIXTIME(p2.dateline)
= (SELECT MAX(FROM_UNIXTIME(dateline))
FROM Post
WHERE threadid = 1
);

It seems that MySQL 5.x accept ORDER BY and LIMIT in a Subquery.
So, this might be worth to try.

SELECT threadid, firstpostid, lastpostid
FROM (SELECT postid, threadid
FROM Post
WHERE threadid = 1
ORDER BY FROM_UNIXTIME(dateline) ASC LIMIT 1
) p1(firstpostid, threadid)
, (SELECT postid
FROM Post
WHERE threadid = 1
ORDER BY FROM_UNIXTIME(dateline) DESC LIMIT 1
) p2(lastpostid);