Need help with a query

[MuSuL]

I'm looking to write a script that will change all the IP addy's of a usergroup when run. I kinda have an idea how to do it but not 100% sure. This is what I've come up with.

UPDATE post
SET ipaddress = '0.0.0.0'
WHERE userid in
(
SELECT post.userid
FROM [user] INNER JOIN post ON user.UserID = post.userid
WHERE groupid = 5
)

Would this work?