//Example:
Table name: users
columns: username, password
default username and password I want to always remain in table 'users'
username=dames and password=:password
//End of Example

DELETE
  u1
FROM
  user u1
LEFT JOIN
  user u2
ON
  u1.access = u2.access
WHERE
  u1.name = "current-user" AND
  ((u1.name != u2.name AND u1.access = "admin") OR (u1.access != "admin"));

if ($user_to_delete == $current_logged_in_user) {
   // Sorry, you can't delete yourself...
}

// In the config file...
$super_admins = array("you", "someone_else");

if (in_array($user_to_delete, $super_admins)) {
  // Sorry, you can't delete a super-admin from the UI.
  // Delete him from the application config first...
}

define('SUPER_ADMIN', 'you');