php mysql comparing two rows in two columns for username and passwort

Hello,

i am writing a small login script for a website.

The username and passwort are stored in a database in two separate columns.

I have it like this:

while($dbbenutzer = mysql_fetch_row($sqlbenutzername))
        while($dbpasswort = mysql_fetch_row($sqlpasswort)){


           echo $dbbenutzer[$i];
           echo $dbpasswort[$j];
       if($benutzername == $dbbenutzer and $pass == $dbpasswort){
         echo '<p>Sie haben sich erfolgreich angemeldet</p>';
         echo '<a href="willkommen.html">Willkommen</a>';
              }
        }

       }

Sice the values are entries in rows in two columns, i use
mysql_fetch_row to get the entries.

Then i want to compare the returned values of the sql statement with
the values provided by the user.

My problem now is only get the first value pair of username and
passwort, not the second.
For instance the first value pair is moritz 123456 which i get
returned but i dont get returned the second value pair thomas thorr.

thank you
yours sincerly
Alexander Schunk