Prevent updating column if null or empty variable in PDO

Question

I am trying to have an update field that admin can update user information. I am stuck at the password. If I update now and leave the password blank then it hashes the blank value and inserts it into DB. I want to keep previous value unless changed on the form.

I looked at this as it was closest to what I am looking for PHP MYSQL -> UPDATE column with variable if that variable isn't null or empty This did not answer my question. unless I have multiple queries I guess with if statements. Really I only want it to update edited fields.

if(isset($_POST['register'])){

    error_reporting(E_ERROR | E_PARSE | E_CORE_ERROR);

    $username = !empty($_REQUEST['username']) ? trim($_REQUEST['username']) : null;
    $pass     = !empty($_REQUEST['password']) ? trim($_REQUEST['password']) : null;
    $fname    = !empty($_REQUEST['fName']) ? trim($_REQUEST['fName']) : null;
    $lname    = !empty($_REQUEST['lName']) ? trim($_REQUEST['lName']) : null;
    $role     = !empty($_REQUEST['role']) ? trim($_REQUEST['role']) : null;
    $region   = !empty($_REQUEST['region']) ? trim($_REQUEST['region']) : null;
    $district = !empty($_REQUEST['district']) ? trim($_REQUEST['district']) : null;
    $id       = !empty($_REQUEST['ID']) ? trim($_REQUEST['ID']) : null;
    $location = !empty($_REQUEST['store']) ? trim($_REQUEST['store']) : null;
    $outlet   = !empty($_REQUEST['outletid']) ? trim($_REQUEST['outletid']) : null;

    $passwordHash = password_hash($pass, PASSWORD_BCRYPT, array("cost" => 12));

    $sql=$pdo->prepare("UPDATE users
                          SET username = :username,
                          password     = :password,
                          fName        = :fName,
                          lName        = :lName,
                          role         = :role,
                          region       = :region,
                          district     = :district,
                          outlet_id    = :outlet_id,
                          store_name   = :store_name
                        WHERE id = :id
                        ");
    $sql->bindParam(':username',$username);
    $sql->bindParam(':password',$passwordHash);
    $sql->bindParam(':fName',$fname);
    $sql->bindParam(':lName',$lname);
    $sql->bindParam(':role',$role);
    $sql->bindParam(':region',$region);
    $sql->bindParam(':district',$district);
    $sql->bindParam(':id',$id);
    $sql->bindParam(':outlet_id',$outlet);
    $sql->bindParam(':store_name',$location);

    if($sql->execute()){
    $_SESSION['success'] = "Successfully Updated Record";
    }// End of if profile is ok
    else{
    print_r($sql->errorInfo()); // if any error is there it will be posted
    $msg=" Database problem, please contact site admin ";
    }


}

I tried using CASE within the statement but that throws an error. How can I update user data without removing data in the column?

IE: If username is changed then just edit that field in the DB. If username and password are changed update both.

Thank you guys

EDIT:

I tried this

    if(!empty(trim($_REQUEST['password']))){
      $passwordHash = password_hash($pass, PASSWORD_BCRYPT, array("cost" => 12));
    }

This still updates the password

Edit2:

"UPDATE users
                          SET username=:username,
                          password = CASE
                                      WHEN :password = '' THEN password
                                      ELSE :password
                                   END,
                          fName=:fName,
                          lName=:lName,
                          role=:role,
                          region=:region,
                          district=:district,
                          outlet_id=:outlet_id,
                          store_name=:store_name
                        WHERE id=:id");

Answer 1

It is right approach. But you should also use else method, to keep password same, if password field is empty.

If you want to update your profile:

$userSql = $pdo->prepare("SELECT * FROM users where id = :id");
$userSql->bindParam(':id',$id);
$userSql->execute();
$user = $userSql->fetch();

if(trim($_REQUEST['password']) !== ''){
    $passwordHash = password_hash($pass, PASSWORD_DEFAULT);
} else {
    $passwordHash = $user['password']; //user password from db
}