这SQL Update语句没报错有什么更新不了

   protected void Button1_Click(object sender, EventArgs e)

    {

        string insert = "insert into my(title,Descriptionp,Keywords,Telephone,Email,createdata)values(@title,@Descriptionp,@Keywords,@Telephone,@email,@createdata)";

        string update = "UPDATE [My] SET [title] = @title, [Descriptionp] = @Descriptionp, [Keywords] = @Keywords,  [telephone] = @telephone, [email] = @email";

        string sel = "select * from [my]";

        string connstring = WebConfigurationManager.ConnectionStrings["qiluConnectionString"].ConnectionString;

        SqlConnection conn = new SqlConnection(connstring);

        conn.Open();

        SqlCommand cmd = new SqlCommand(sel, conn);

        try

        {

            cmd.Parameters.Add("@title", SqlDbType.VarChar).Value = title.Text.Trim();

            cmd.Parameters.Add("@Descriptionp", SqlDbType.VarChar).Value = Descriptionp.Text.Trim();

            cmd.Parameters.Add("@Keywords", SqlDbType.VarChar).Value = keywords.Text.Trim();

            cmd.Parameters.Add("@Telephone", SqlDbType.VarChar).Value = telephone.Text.Trim();

            cmd.Parameters.Add("@email", SqlDbType.VarChar).Value = email.Text.Trim();

            cmd.Parameters.Add("@createdata", SqlDbType.VarChar).Value = DateTime.Now;

            SqlDataReader rea = cmd.ExecuteReader();

            if (!rea.Read())

            {

                rea.Close();

                cmd.CommandText = insert;

                cmd.ExecuteNonQuery();

                Page.ClientScript.RegisterStartupScript(this.GetType(), "kk", "<script>alert('成功(*^ _ ^*)')</script>");

            }

            else

            {

                rea.Close();

                cmd.CommandText = update;

                cmd.ExecuteNonQuery();

                Page.ClientScript.RegisterStartupScript(this.GetType(), "kk", "<script>alert('更新成功')</script>");

            }

        }

        catch

        {

            Page.ClientScript.RegisterStartupScript(this.GetType(), "kk", "<script>alert('数据插入失败，请检查输入是否正确或申请技术支持')</script>");

        }

        finally

        {

            cmd.Dispose();

            conn.Close();

        }

    }