我不能在c＃中解決這個錯誤？

Question

我'得到以下錯誤：

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near "temp" at line 1.

下面的代碼：

public void DeleteColumn(string columnName) 
{ 
    try 
    { 
     query.CommandText = "alter table publisher drop @col "; 
     query.Prepare(); 
     query.Parameters.AddWithValue("@col", columnName); 
     query.ExecuteNonQuery(); 
     Console.WriteLine("column deleted successfully"); 
     transaction.Commit(); 
     Console.WriteLine("successfully committed to database"); 
    } 
    catch (MySqlException ex) 
    { 
     Console.WriteLine(ex.Message); 
    } 
} 

我這是在傳遞DeleteColumn值：

DeleteColumn("temp"); 

沒有連接問題，我已經定義了每個需要的值

Answer 1

你需要一個column添加到您的drop語句

query.CommandText = "alter table publisher drop column @col "; 

Answer 2

爲什麼你期望你的代碼是不工作：

您在給定的查詢按照mysql語法有錯誤;正確的語法使用alter table如下：刪除列：

ALTER TABLE "table_name" 
DROP "column_name"; 

解決方案

更改您的CommandText如下所示：

query.CommandText = "alter table publisher DROP COLUMN @col "; 

和參數將是這樣的：

query.Parameters.AddWithValue("@col", columnName);//passed value to the function this must be the column name. 

因此，你的tr y塊將是：

try 
    { 
     query.CommandText = "alter table publisher DROP COLUMN @col ";  
     query.Parameters.AddWithValue("@col", columnName); 
     int result=query.ExecuteNonQuery(); 
     transaction.Commit(); 
     if(result>0) 
     Console.WriteLine("column deleted successfully"); 
     else 
     Console.WriteLine("successfully committed to database"); 
    } 

Answer 3

SQL查詢語法是錯誤的，使用這個。

query.CommandText = "alter table publisher DROP COLUMN @col ";