输入类型文件与准备好的语句

form

<form method="post" enctype="multipart/form-data" action="editupload.php">
            <div class="fields">
                <label >Title of the Story :</label>
                <input type="text" class="formfield storytitle" placeholder="Enter story's Title" value="<?php echo $row['title']; ?>" name="title"/>
            </div>

            <div class="fields">
                <label>Select an Image :</label>
                <input type="file" name="image" />
            </div>
            <input type="submit" style="width:40%; margin: 0 30% 0 30%;"name="contentupload" value="Upload Edit" />  
        </form>

this form is used to edit the data which is inserted into a mysql table.

part of editupload.php file

Include('connect.php');
    $query=$handler->prepare("UPDATE ".$college." SET title=?,image=?,imagename=? WHERE id=?");
    $query->execute(array($title,$image,$imagename,$storyid));
    if($query->rowCount())
    {
        echo "content uploaded!";

    }
    else
    {
        echo "content not uploaded!";
    }

Now what happens whenever i want to edit a row with title

value="<?php echo $row['title']; ?>"

then if i select image also with changed title then only the data is uploaded otherwise if i do not select the image and only changes title then it doesn't uploades the data

so how to make input "type file" (mysql column as longblob) as if there is no file selected then also the data should be updated without changing the previously inserted image or give input "type file" a value as given to title that is the previously uploaded image?