如何将byte []转换为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回报良好或“否”或月

在C＃if(month = '', 'NO',month) as monthT返回byte[]，但我需要回到NO如果一个月为空，否则返回month。

我的C＃代码如下所示：

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

虽然研究我发现，有使用CAST VARCHAR的bug。解决方案是使用CHAR而不是VARCHAR。

证明链接：

Using Conversion Functions

Bug #34564 CAST does not accept varchar type

Cast Functions and Operators

Answer 2

我没有mysql专家，但你为什么不尝试投？

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

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