Question

我有2个表，即customers表和orders表。基本上我的问题是它总是给我一个错误，这是'未知字段列表'。我试过在phpmyadmin XAMPP它的工作唯一的问题是当我在VS studio c＃中使用它时它给了我一个错误。我很困惑后面的嘀嗒声'''不起作用，但后面的滴答声在localhost上起作用。请帮帮我。

这是我的sql语法：

SQL = "SELECT o.`Order ID`, o.Description, o.Amount 
       FROM tbl_orders AS o 
           INNER JOIN tbl_customers AS c ON o.`Order ID` = c.`Order ID` 
       WHERE c.`Customer ID` = '" + cust_id + "'";
            cmd.Connection = dbCon;
            cmd.CommandText = SQL;
            rdr= cmd.ExecuteReader();
            dt.Load(rdr);

Answer 1

尝试删除并重新输入列名周围的`，以防它没有正确复制。还要尝试在字符串之前放一个@。

SQL = @"<the sql>";

这适用于mysql xampp

 MySqlConnection sqlConnection = new MySqlConnection(@"Server=localhost;Database=test;");
        var sql = @"SELECT o.`Order ID`, o.Description, o.Amount 
   FROM tbl_orders AS o 
       INNER JOIN tbl_customers AS c ON o.`Order ID` = c.`Order ID` 
   WHERE c.`Customer ID` = 1";
        sqlConnection.Open();
        MySqlCommand sqlCommand = new MySqlCommand(sql,sqlConnection);
        sqlCommand.ExecuteNonQuery();
        sqlConnection.Close();

Answer 2

名称中带有空格的列应括在方括号中。

尝试

SQL = "SELECT o.[Order ID], o.Description, o.Amount 
       FROM tbl_orders AS o 
           INNER JOIN tbl_customers AS c ON o.[Order ID] = c.[Order ID] 
       WHERE c.[Customer ID] = '" + cust_id + "'";
            cmd.Connection = dbCon;
            cmd.CommandText = SQL;
            rdr= cmd.ExecuteReader();
            dt.Load(rdr);

http://tinyurl.com/qcf45vf

What is the use of the square brackets [] in sql statements?

带有空格的Mysql内连接列

2 个答案: