query.dart

//return all persons from the database
  Future<List<Person>> getAllPersons() async {
    final db = await database;
    var response = await db.query("Person");
    List<Person> list = response.map((c) => Person.fromMap(c)).toList();
    return list;
  }

//return single person with id
 Future<Person> getPersonWithId(int id) async {
    final db = await database;
    var response = await db.query("Person", where: "id = ?", whereArgs: [id]);
    return response.isNotEmpty ? Person.fromMap(response.first) : null;
  }