SQL“关键字'from'附近的语法不正确。”

Question

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Configuration;

namespace RockPaperApp
{
  public partial class WebForm1 : System.Web.UI.Page
  {
    protected void Page_Load(object sender, EventArgs e)
    {
        if (Session["New"] != null)
        {
            Response.Redirect("/Game.aspx");
        }
    }

    protected void RegButton_Press(object sender, EventArgs e)
    {
        Response.Redirect("/Register.aspx");
    }

    protected void LogButton_Press(object sender, EventArgs e)
    {
        string username = UsernameLogTxt.Text;

        try
        {
            string conn = ConfigurationManager.ConnectionStrings["UserConS"].ToString();
            string CommandText = "pword from data Username=@username";

            using (SqlConnection connection = new SqlConnection(conn.ToString()))
            using (SqlCommand command = new SqlCommand(CommandText, connection))
            {
                command.Parameters.AddWithValue("@username", username);
                connection.Open();

                using (SqlDataReader reader = command.ExecuteReader())
                {
                    while (reader.Read())
                    {
                        string realpass = reader[0].ToString();

                        if (realpass != PasswordLogTxt.Text)
                        {
                            Response.Write("<span style='color:red'>A Wrong Username of Password has been entered.</span>");
                        }
                        else
                        {
                            Session["New"] = UsernameLogTxt.Text;
                            Response.Redirect("/Game.aspx");
                        }
                    }

                    if (!reader.HasRows)
                    {
                        Response.Write("No such username exists.");
                    }
                }
                connection.Close();
            }

        }
        catch (SqlException ex)
        {
            Response.Write( ex.Message);
        }
    }

    protected void Button1_Click(object sender, EventArgs e)
    {
        Response.Redirect("Register.aspx");
    }
  }      
}

Answer 1

这不是有效的SQL查询：

"pword from data Username=@username"

也许当您打算复制/粘贴整个查询时，您复制/粘贴了部分查询？不过，它看起来甚至不像是查询的有效部分。

错误告诉您问题出在关键字from，因为这是错误发生后遇到的第一件事。对于SQL错误，总是查看错误位置之前解析的最后一件事，最后一件事是导致错误的原因。在本例中，关键字pword引起了这个问题，因为这在SQL中不是有效的关键字或标识符，查询解析器无法理解它。