Question

我正在尝试获取帐户表的行数，以便我可以登录帐户，但MySQL参数不会添加值。

这是我的代码：

public int MyMethod(string username, string password)
{
    int count = 0;
    string query = "SELECT * FROM accounts WHERE username = '?user' AND password = '?pass' LIMIT 1;";

    using (MySqlCommand cmd = new MySqlCommand(query, connector))
    {
        cmd.Parameters.Add(new MySqlParameter("?user", username));
        cmd.Parameters.Add(new MySqlParameter("?pass", password));

        count = int.Parse(cmd.ExecuteScalar().ToString());
    }

    return count;
}

Answer 1

参数占位符不应该用单引号括起来，因为它会强制它成为值而不是参数，试试这个，

public int MyMethod(string username, string password)
{
    int count = 0;
    string query = "SELECT * FROM accounts WHERE username = @user AND password = @pass LIMIT 1;";

    using (MySqlCommand cmd = new MySqlCommand(query, connector))
    {
        cmd.Parameters.Add(new MySqlParameter("@user", username));
        cmd.Parameters.Add(new MySqlParameter("@pass ", password));

        connector.Open(); // don't forget to open the connection
        count = int.Parse(cmd.ExecuteScalar().ToString());
    }

    return count;
}

Answer 2

我相信你想做这样的事情：

SELECT COUNT(*) FROM accounts WHERE username = '?user' AND password = '?pass';

这将为您提供具有指定用户名和密码的记录数。

Answer 3

尝试添加如下参数：

cmd.Parameters.AddWithValue("@user", username);
cmd.Parameters.AddWithValue("@pass", password);

Answer 4

试试这个： @myVariable 而不是'？myVariable'， SELECT COUNT（*）而不是 SELECT *

public int MyMethod(string username, string password)
{
  int count = 0;
  string query = "SELECT count(*) FROM accounts WHERE username = @user AND password = @pass LIMIT 1;";

   using (MySqlCommand cmd = new MySqlCommand(query, connector))
   {
      connector.Open(); 
      cmd.Parameters.AddWithValue("@user", username);
      cmd.Parameters.AddWithValue("@pass", password);       
      count = int.Parse(cmd.ExecuteScalar().ToString());
   }

   return count;
}

MySQL参数不添加值

4 个答案: