[squidsk]

You can just grab all threads/posts that don't exist. You can alter the above queries as follows:

INSERT INTO post
(SELECT *
FROM post7
WHERE NOT threadid IN (SELECT threadid FROM thread))

INSERT INTO thread
(SELECT *
FROM thread7
WHERE NOT threadid IN (SELECT threadid FROM thread))

EDIT: You have to do the post query first otherwise the deleted thread will already be restored in the thread table.