Consolidate Users

BACKUP YOUR DATABASE BEFORE FOLLOWING THESE INSTRUCTIONS
It’s a single SQL command to change the post authors for all your posts. Using phpMyAdmin (or the MySQL interface of your choice), try this:
update wp_posts set post_author=1;
That’ll set the default WP admin user as the author of all your posts. Confirm this worked correctly, then feel free to delete your other users.

Ahh – thanks. I was hoping it could be done through the WP admin interface – unfortunately, my web host does not provide phpMyAdmin. Are there any MySQL interfaces that I can just install myself?

If you have shell access to your host, you can use the mysql command-line tool:
$ mysql -u<username> -p
Password: <enter password>
mysql> use <WP database>;
mysql> update wp_posts set post_author=1;
mysql> quit;
Or you could whip up a quickie PHP file to do it for you, and upload it to your wp-admin directory:
<?php
require('../wp-blog-header.php');
$sql = "update wp_posts set post_author=1;";
$result = $wpdb->get_result($sql);
echo $result;
?>

Wow, thanks skippy! Now, before I run this, would I be able to do a select to make sure that I’m setting the posts to the correct user? Something like:
<?php
require('../wp-blog-header.php');
$sql = "select distinct post_author from wp_posts;";
$result = $wpdb->get_result($sql);
echo $result;
?>

You could include as much conditional logic as you want. The select statement you provide would only report the unique userIDs assigned to each current post. As I read your original message, it sounded like you already knew who the author was, and it was incorrect — thus this discussion.
UserID #1 is always your default WordPress administrator. If you don’t want all posts to belong to the admin, just substitute whatever userID you need into the query I provided.

I’m pretty sure it’s #1 that I want to set them to – I’m just being paranoid. I work in QA – LOL.
Thanks for the help!

How to you delete a user?