Nefunguje Select když použiji Inner Join

$dotaz ="SELECT login.jmeno_u, jmeno, prijmeni, email FROM  login INNER JOIN registrace ON login.jmeno_u=registrace.jmeno_u";
         $prubeh = $db -> query($dotaz);
         echo("<table class=\"table table-hover\">
                   <tbody>
                   <tr>
                    <td>Uživatelské jméno je:</td>
                    <td>Jmeno</td>
                    <td>Příjmení</td>
                    <td>Email je:</td>
                    <td>&nbsp;</td>
                    </tr>
                   </tbody>");
         while($row = $prubeh -> fetch_assoc())
         {
           if($row['jmeno_u'] !== "Admin")
          {
          echo ("<form method=\"post\">
                   <tr>
                    <td><input name=\"jmeno_u\" type=\"hidden\" value=\"". $row['jmeno_u'] ."\" />". $row['login.jmeno_u'] ."</td>
                    <td>". $row['jmeno'] ."</td>
                    <td>". $row['prijmeni'] ."</td>
                    <td>". $row['email'] ."</td>
                    <td><button type=\"submit\"><img src=\"css/obrazky/x.png\" style=\"width: 25px; height: 25px \"></td>
                    </tr>
                 </form>");
          }
         }
         echo("</table>");