Как преобразовать байт [] в varchar?

SELECT Trainer.id AS idTrainer, surname, lastname, name,  
if(month = '', 'NO',month) as monthT, quarter, halfyear, year, id_Person, photo
FROM Trainer, Person
WHERE Trainer.id_Person = Person.id

if (month = '', 'NO', month) as monthT в phpmyadmin return good or 'no' or month

В C # возвращает байт [] , но мне нужно вернуть NO , если месяц пуст, или вернуть месяц .

Мой код C # выглядит следующим образом:

string sql = @" SELECT Trainer.id AS idTrainer, surname, lastname, name,  if(month = '', 'NO',month) as monthT, quarter, halfyear, year, id_Person, photo
                FROM Trainer, Person
                WHERE Trainer.id_Person = Person.id";
using (MySqlConnection connection = ConnectToDataBase.GetConnection())
{
    MySqlCommand command = new MySqlCommand(sql, connection);
    MySqlDataAdapter adapter = new MySqlDataAdapter();

    connection.Open();
    adapter.SelectCommand = command;
}