I changed my user name and now can't get updates
I changed my apple id and now when I try to get updates or purchases for old games bought it says I can't do it because they were purchased under different ID. How do I link the two.
iPad Mini, iOS 8
Did you create a new account or updated the primary email address on your existing account ?
All content is tied to the account that downloaded it, if you created a new account then you only your old account will be able to download updates to your old account's apps (and potentially redownload its purchases) - you can't merge accounts or transfer content between them.
If you updated your existing account with a new primary email address then you should be able to download updates to your apps with the new updated version. If your old id is still showing on your iPad then try logging out (tap on your id at the bottom of the Featured tab in the App Store app) and back into the account.