我有两张table。。。只有$sql正在执行。我如何得到$sql2来查询呢$sql2正在数据库中存储带有当前时间戳的secondid，但没有从“serialnumber”接收任何输入。只有第一个$sql正在数据库中查询和存储。

+--------------+
       | SafetyAtt    |       
       +--------------+             
       | SecondID    |
       | SerialNumber |
       +--------------+                    

          +---------+
          | Safety  |
          +---------+
          | ID      |
          | DateLog |
          | Topic   |
          +---------+

      <table>
        <thead>
        <tr align="left">
          <th>Seq</th>
          <th>Date</th>
          <th>Topic</th>
          <th># of Attendees</th>
          <th>Add Attendee</th>
        </tr>
        </thead>

    <?php
  $sql = "SELECT ID, DateLog, Topic FROM Safety";
  $sql2 = "SELECT secondID, SerialNumber FROM SafetyAtt";
  $result = $conn->query($sql);
  if (!$result) {
    trigger_error('Invalid query: ' . $conn->error);
  }

  if ($result->num_rows > 0) {
   // output data of each row
   while($row = $result->fetch_assoc()) {
    echo "<tr><td>" . $row["ID"]. "</td><td>" . $row["DateLog"] . "</td><td>"
    . $row["Topic"] . "</td><td>" . $row["secondID"] . "</td><td>"  ?>
      Serial Number: <input type="text" name="serialnumber" placeholder="Enter serial #"> <?php " . </td></tr>";
    }
    echo "</table>";
  } else {
   echo "0 results"; 
   }
  $conn->close();
    ?>

</table>