mysql查询中如何避免like语句为空

在下面的代码中,我一直在查询数据库中的姓名和电子邮件, 在这种情况下,如果name或email为空,它将获取所有数据。

如何避免这种情况?请帮忙

MySQL查询:

$searchdata = mysqli_query($this->dbh, "SELECT insertdata.name, insertdata.email, state.StateName, district.DistrictName
  FROM insertdata
  INNER JOIN state ON insertdata.state = state.StCode
  INNER JOIN district ON insertdata.district = district.DistCode
  WHERE name LIKE '%$namesearch%' OR email LIKE '%$emailsearch%'");

我的密码,

<?php
include_once("function.php");
$searchdata=new DB_con();
if(isset($_POST['submit']))
{
    $namesearch=$_POST['namesearch'];
    $emailsearch=$_POST['emailsearch'];
}
$search=$searchdata->searchdata($namesearch,$emailsearch);
foreach($search as $search)
{
    ?>
    <tr>
    <td><?php echo ($search['name']);?></td>
    <td><?php echo ($search['email']);?></td>
    <td><?php echo ($search['StateName']);?></td>
    <td><?php echo ($search['DistrictName']);?></td>
    </tr>
<?php 
}
?>