Double booking

[wsrta]

Can someone please help me I'm stuck with the validation of the room reservation. The room reservation should not double book a room how can I achieve this? 

 <?php

            $sql = "SELECT * FROM studentrequest";

            $result = mysqli_query($conn,$sql);

            if($result){

              while($row = mysqli_fetch_assoc($result)){

                $srequestid = $row['studentrequestid'];

                $studentid = $row['studentID'];

                $studentname = $row['studentName'];

                $roomnumber = $row['roomNumber'];

                $instructor = $row['instructor'];

                $dateuse = $row['dateUsed'];

                $ts = $row['timeStart'];

                $te = $row['timeEnd'];

                echo '      

                <tr>

                <th scope="row">'.$srequestid.'</th>

                <td>'.$studentid.'</td>

                <td>'.$studentname.'</td>

                <td>'.$roomnumber.'</td>

                <td>'.$instructor.'</td>

                <td>'.$dateuse.'</td>

                <td>'.$ts.'</td>

                <td>'.$te.'</td>

              </tr>';

              }

            }

          ?>

        </tbody>

      </table>

          </main>

</body>

</html>

<?php

[Barand]

This tutorial may help