Laravel Updates existing DB values to NULL

I'm trying to Update Form Values that have multiple form Fields. Everything works well only while Updated DB laravel updates null values in DB, which removes existing data in the field.

My controller receives form field requests. When the record is present e.g. three and fFour holds old values in DB, and I try to only update one and two fields it also updates three and four to null as I only send one and two values.

public function updateSystemSettings(Request $request){
    // Validate Request
    $validator = Validator::make($request->all(), [
        'one' => 'string|nullable',
        'two' => 'string|nullable',
        'three' => 'json|nullable',
        'four' => 'json|nullable',
        etc.. other null or holds values
    ]);
    if($validator->fails()){
        return response()->json($validator->errors()->toJson(), 400);
    }

    // Get First Row if Exist ELSE I will create record
    $systemSettings = SystemSettings::first();
    // Update
    $result = array_filter(request()->all());
    SystemSettings::where('id', $systemSettings->id)->update([
        "one" => $result['one'],
        "two" => $result['two'],
        "three" => $result['three'],
        other fields...
    ]);

    // After update Send Updated Dat
    $data = SystemSettings::first();
    $response = json_decode($data, JSON_UNESCAPED_SLASHES);
    return response()->json([
        'data' => $response
    ]);
}

Tried almost everything, in SQL we have something called values(?, ?, ?, ?, ? ) which only updates the fields which has values else it keeps the old DB values as is.

I think you have to check if the request has the key (e.g. three):

SystemSettings::where('id', $systemSettings->id)->update([
    "one" => $result['one'] ?? $systemSettings->one,
    "two" => $result['two'] ??  $systemSettings->two,
    "three" => $result['three'] ??  $systemSettings->three,
    other fields...
]);

FYI:

"one" => $result['one'] ?? $systemSettings->one

is eqaul to

"one" => $result['one'] ? $result['one'] : $systemSettings->one