MySQL on Select

I am trying to select all data from a table. I have a Database "registered_users" that has a table "user_email" I want to check all. as it checks to see if email is registered nad then redirect to a page... Right now it is selecting from the last one that has been inputted. I want to check all emails for every ID

    $querygetusermain = "SELECT * FROM registered_users";
$resgetusermain   = mysql_query($querygetusermain);

    $reals = "SELECT * FROM `registered_users` ORDER BY `registered_users`.`id`  DESC LIMIT 0,1";
    $realss   = mysql_query($reals);
    $realssrow   = mysql_num_rows($realss);
    while($realssss= @mysql_fetch_array($realss)){
$register = $realssss['user_email'];