Problemer med udtræk

$sql = "SELECT ".$db_table_prefix."Users.Username,".$db_table_prefix."Logins.SignIn
                FROM ".$db_table_prefix."Users INNER JOIN ".$db_table_prefix."Logins
                ON ".$db_table_prefix."Users.User_ID = ".$db_table_prefix."Logins.Login_ID";

$result = $db->sql_query($sql);

while ($row = $db->sql_fetchrow($result))
{
echo $row['Username'];
}
$db->sql_freeresult($result);