How to prevent null values to updating MySQL database - mysql

Question

My update query is
"UPDATE registration SET `dob` = '".$theDate."' , pwd='".$_REQUEST['n_password']."', name='".$_REQUEST['n_name']."' where id='".$_SESSION['id']."' "
Problem is that it is not necessary that user update all fields so if it happens there are null values coming from form and it will replace earlier value in database.
I can update it one by one after checking if field value is not null but if there is any other way r tutorial please help me

Answer 1

I can update it one by one after checking if field value is not null
but if there is any other way r tutorial please help me
Don't issue an UPDATE query after you check each value, instead add that column to the query you're building, then execute just one UPDATE with only the columns that had values.
$dbh = new PDO('mysql:host=localhost;dbname=whatever', 'user', 'password');
$params = array();
$sql = "UPDATE REGISTRATION SET `dob` = ?";
$params[] = $theDate;
if (!empty($_REQUEST['n_password'])) {
$sql .= ", `pwd` = ?";
$params[] = $_REQUEST['n_password'];
}
if (!empty($_REQUEST['n_name'])) {
$sql .= ", `name` = ?";
$params[] = $_REQUEST['n_name'];
}
$sql .= " WHERE `id` = ?";
$params[] = $_SESSION['id'];
$stmt = $dbh->prepare($sql);
$stmt->execute($params);