PHP Exception: multi-operators

I tried take user-level from my database, and check what the level of the user. When I try do this:

include "../web/config.php";
            $adminTrueQuery = mysql_query("SELECT * FROM `users` WHERE `Username` = '$admin_username' AND `Password` = '$admin_password' LIMIT 1;");
            $adminLevel = mysql_fetch_array($adminTrueQuery);
            $adminLevel = $adminLevel['Level'];
            if($adminLevel !== "c" || "b") {
                throw new Exception ("You don't admin {$adminLevel}"); // return
            }

I get an error. And

$adminLevel = "c";

What the problem?