如何將byte []轉換爲varchar？

Question

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 

在phpMyAdmin回報良好或「否」或月

在C＃if(month = '', 'NO',month) as monthT返回byte[]，但我需要回到NO如果一個月爲空，否則返回month。

我的C＃代碼如下所示：

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; 
} 

Answer 1

雖然研究我發現，有使用CAST VARCHAR的bug。解決方案是使用CHAR而不是VARCHAR。

證明鏈接：

Using Conversion Functions

Bug #34564 CAST does not accept varchar type

Cast Functions and Operators

Answer 2

我沒有mysql專家，但你爲什麼不嘗試投？

CAST(if(month = '', 'NO',month) AS VARCHAR) AS monthT 

更多在這裏： http://dev.mysql.com/doc/refman/5.0/en/cast-functions.html