I noticed on one of my WordPress installs I have two admin authors with the same email address. Both of them have posts attributed to them. They are both for the same person, so I'd like to combine the two accounts into one. How can I do this?
Delete one account.
Upon deletion WP will prompt you with a question of whether to delete all posts by said author or attribute them to another user.
Simple as that, wanted functionality is provided by the core.