我如何从数据库中读取单列值 [英] how can i read the single column value from database

问题描述

我想读为....

i m trying to read as....

string a;
cmd = new SqlCommand("select role from temp where (emp_id=''" + txtUserId.Text + "'' and paswrd=''" + txtPwd.Text + "'')",cn);
                    a = cmd.ExecuteReader().Read().ToString();
                    Console.Write(a);

....它没有给出任何错误...但是"a"中没有值....
请帮助

.... it is not giving any error ... but no value is coming in "a"....
pls help

推荐答案

尝试:

cmd = new SqlCommand("select role from temp where (emp_id='" + txtUserId.Text + "' and paswrd='" + txtPwd.Text + "')",cn);
SqlDataReader reader = cmd.ExecuteReader().Read().ToString();
if (reader.Read())
   {
   Console.Write((string) reader["role"]);
   }

或者更好的是，使用参数化查询并阻止人们使用SQL Injection破坏您的数据库:

Or, better, use parametrised queries and stop people destroying your database with SQL Injection:

cmd = new SqlCommand("select role from temp where (emp_id=@ID and paswrd=@PW)",cn);
cmd.Parameteres.AddWithValue("@ID", txtUserId.Text);
cmd.Parameteres.AddWithValue("@PW", txtPwd.Text);
SqlDataReader reader = cmd.ExecuteReader().Read().ToString();
if (reader.Read())
   {
   Console.Write((string) reader["role"]);
   }

更好的是，永远不要以纯文本形式存储密码！这里有一条提示说明:密码存储:操作方法. [^ ]


您是否可以通过SqlDataAdaptor来提供解决方案..

谢谢"


您的最后一个奴隶死于什么?

Even better, don''t ever store passwords in straight text! There is a Tip here that explains that: Password Storage: How to do it.[^]


"can u provaide the solution through SqlDataAdaptor..

thanks"


What did your last slave die of?

using (SqlConnection connection = new SqlConnection(strConnect))
    {
    SqlDataAdapter da = new SqlDataAdapter();
    da.SelectCommand = new SqlCommand("SELECT role FROM temp WHERE emp_id=@ID AND paswrd=@PW", connection);
    da.SelectCommand.Parameters.AddWithValue("@ID", txtUserId.Text);
    da.SelectCommand.Parameters.AddWithValue("@PW", txtPwd.Text);
    DataTable dt = new DataTable();
    da.Fill(dt);
    }

请尝试以下操作:-

Please try this:-

string a;
cmd = new SqlCommand("select role from temp where (emp_id=''" + txtUserId.Text + "'' and paswrd=''" + txtPwd.Text + "'')",cn);
a = cmd.ExecuteScalar().ToString();
Console.Write(a);

希望这对您有帮助

http://www.diranieh.com/Netado/DataAdapters.htm [

Hope This Will Help You

http://www.diranieh.com/Netado/DataAdapters.htm[^]

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