Error query failed , check manual line 3 - php

Question

My upload.php and view.php are working fine but I am not able to create a download links to download files. db name = dbtuts.
and the link for download option is:
<td><a href='download.php?id=<?php echo $row['file_name']; ?>'>Download</a></td>
Here is the code for download.php
<?php
// Make sure an ID was passed
if(isset($_GET['id'])) {
// Get the ID$id
$file_name= ($_GET['id']);
// Make sure the ID is in fact a valid ID
if($file_name == NULL) {
die('The name is invalid!');
}
else {`enter code here`
// Connect to the database
$dbLink = new mysqli('localhost', 'root', "", 'dbtuts');
if(mysqli_connect_errno()) {
die("MySQL connection failed: ".mysqli_connect_error());
}
// Fetch the file information
$query = "
SELECT file, type, size
FROM tbl_uploads
WHERE `file` = {$file_name}";
$result = $dbLink->query($query);
if($result) {
// Make sure the result is valid
if($result->num_rows == 1) {
// Get the row
$row = mysqli_fetch_assoc($result);
header("Content-Type: ".$row['type']);
header("Content-Length: ".$row['size']);
header("Content-Disposition: attachment");
// disopsition = attachment to force download request
// Print data
echo $row['data'];
}
else {
echo 'Error! No file exists with that ID.';
}
// Free the mysqli resources
#mysqli_free_result($result);
}
else {
// if there is an error excuting the query
echo "Error! Query failed: <pre>{$dbLink->error}</pre>";
}
// close database connection
#mysqli_close($dbLink);
}
}
else {
// if no ID passed
echo 'Error! No ID was passed.';
}
?>