Question Mysql question - Offset a value?

[Coume]

Thanks for answering.

btw, I am currently working in a test environment, I can't afford to mess up with my site and data

Strange in the email notification I can see:

UPDATE tablename
SET topic_id = topic_id + 386 Remember, backup first!

but I can't see it reading your post, did you delete this bit?

As my several thousands of de/german and www have similar post_id as they were stored in different tables, I need to offset the german ones by the amount of www ones available to avoid having the German ones overriding the www ones.

www table
post_id = 1
post_id = 2
....
post_id = 125 894
post_id = 125 895
de table
post_id = 1
post_id = 2
....
post_id = 6 704
post_id = 6 705

If I merge the two, the www's post from 1 to 6 705 would get replaced by the German ones, no?

In addition, I also need to update the forum_id as the forum_id =4 on www and on de link to different forums (i.e.: general questions in English and General questions in German), if I merge the two tables without any tweaking when importing the posts, they will all be linked to the wrong forum. So I need to create first, new forums with new IDs in the www one and then replace the old german forum_ids with this new one with something like that I guess:
"UPDATE tablename
SET forum_id = 12
WHERE forum_id = 4"

Does it make sense?