How to Connect a database with two Tables?

using System;
using System.Data;
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;


public partial class Registration : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (IsPostBack)
        {
            SqlConnection con = new SqlConnection(System.Configuration.ConfigurationManager.ConnectionStrings["Test1ConnectionString"].ConnectionString);
            con.Open();

            string cmdStr = "Select count(*) from Registration where UserName='" + TextBoxEA.Text + "'";
            SqlCommand userExist = new SqlCommand(cmdStr, con);
            SqlCommand cmd = new SqlCommand("select * from Registration", con);
            SqlDataReader dr;
           
            dr = cmd.ExecuteReader(CommandBehavior.SingleResult);
            while (dr.Read())
            {
                //....
            } dr.Close();

                SqlCommand insertcmd = new SqlCommand("insert into TableCEO", con);
            SqlDataAdapter dap = new SqlDataAdapter(insertcmd);
            int temp = Convert.ToInt32(userExist.ExecuteScalar().ToString());
            con.Close();
            


            if (temp == 1)
            {
                Response.Write("User Name Already Exist!!!<br /> Please Choose Another User Name.");
            }
        }
    }
    protected void Submit_Click(object sender, EventArgs e)
    {

        SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["Test1ConnectionString"].ConnectionString);
        con.Open();
        

        string insCmd = "Insert into Registration (UserName, Prefix, FirstName, LastName, EmailAddress, Password) values (@UserName, @Prefix, @FirstName, @LastName, @EmailAddress, @Password)";
        SqlCommand insertUser = new SqlCommand(insCmd, con);
        insertUser.Parameters.AddWithValue("@UserName", TextBoxEA.Text);
        insertUser.Parameters.AddWithValue("@Prefix", TextBoxPR.Text);
        insertUser.Parameters.AddWithValue("@FirstName", TextBoxFN.Text);
        insertUser.Parameters.AddWithValue("@LastName", TextBoxLN.Text);
        insertUser.Parameters.AddWithValue("@EmailAddress", TextBoxEA.Text);
        insertUser.Parameters.AddWithValue("@Password", TextBoxPass.Text);

        
        SqlCommand cmd = new SqlCommand("Insert into TableCEO (LastName, FirstName, Prefix, EmailAddress) values (@LastName, @FirstName, @Prefix, @EmailAddress)");
        new SqlCommand(insCmd, con);

        SqlCommand insertcmd = new SqlCommand("insert into TableCEO", con);
        SqlDataAdapter dap = new SqlDataAdapter(insertcmd);
        
        

        
        {
            insertUser.ExecuteNonQuery();
            con.Close();
            

            Response.Redirect("Login.aspx");
        }
       
        {
            
            Response.Write("Something Really Bad Has Happened....Please Try Again.");
        }
        
        {

        }
    }
}