Custom code to return whether or not a user has logged in not working

I am trying to use the code below to figure out if a user has accessed Drupal before, if not true is returned. However, it is not working, is there something I am missing?

global $user; 
$users = db_query("SELECT DISTINCT(uid), access FROM {users} WHERE access = %d AND uid = %s", 0, $user->uid);
$total_users = db_num_rows($users);
if ($total_users == 1)
{
	return true;
}
else { return false; }