I want to insert record like new user then this or existing then this?

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C#3.5

i try to differentiate the user and it's task.
i make windows app in c# about physiotherapy management system.
i want to fetch records from db . there are 2 tables patient_mstr for new user and old_patient for existing user.

i want to do that if user is visited 2nd time then records will be shown from patient_mstr and if visted more than 2nd time then reocrds will be shown from old_patient.

i did another logic which i realize, thank u in advance.

What I have tried:

private void txtsno_KeyDown(object sender, KeyEventArgs e)
{
cn.Open();
try
{

if (e.KeyCode == Keys.Enter)
{
// this query for retrieve just serial number.
OleDbCommand cmdt = new OleDbCommand("select top 1 * from patient_mstr where Contact_no=@Contact_no", cn);
cmdt.Parameters.Add(new OleDbParameter("@Contact_no", txtsno.Text));
// store value in userexist variable.
int UserExist = (int)cmdt.ExecuteScalar();
// this query for visiting numbers.
OleDbCommand vst = new OleDbCommand("select count(*) from patient_mstr where Contact_no=@Contact_no",cn);
vst.Parameters.Add(new OleDbParameter("@Contact_no",txtsno.Text));

// store value in rec variable.
int rec = (int)vst.ExecuteScalar();
//OleDbDataReader dr2 = cmdt.ExecuteReader();
if (UserExist == 1)
{

//if (e.KeyCode == Keys.Enter)
//{
OleDbCommand cmd = new OleDbCommand("select P_name,E_date,Main_pain,Sub_pain,V_charge,Paid,Description from patient_mstr where Contact_no=@Contact_no", cn);
cmd.Parameters.Add(new OleDbParameter("@Contact_no", txtsno.Text));
// cn.Open();
cmd.ExecuteNonQuery();
OleDbDataReader dr = cmd.ExecuteReader();
if (dr.Read())
{
lblapnm.Text = (string)dr["P_name"];
lblapain.Text = (string)dr["Main_pain"] + " , " + (string)dr["Sub_pain"];
lbld.Text = (string)dr["Description"];
//lblcrgh.Text = dr["V_charge"].ToString();
//lblpdinf.Text = dr["Paid"].ToString();
lbladt.Text = dr["E_date"].ToString();
//pb_old.Image = (Image)dr["Image"];

}
dr.Close();
}
else if (UserExist > 1)
{
OleDbCommand cmd = new OleDbCommand("select P_name,E_date,Pain,Description,Image_new from old_patient where Contact_no=@Contact_no", cn);
cmd.Parameters.Add(new OleDbParameter("@Contact_no", txtsno.Text));
// cn.Open();
cmd.ExecuteNonQuery();
OleDbDataReader dr = cmd.ExecuteReader();
if (dr.Read())
{
lblapnm.Text = (string)dr["P_name"];
lblapain.Text = (string)dr["Main_pain"] + " , " + (string)dr["Sub_pain"];
lbld.Text = (string)dr["Description"];
//lblcrgh.Text = dr["Total_charge"].ToString();
//lblpdinf.Text = dr["Total_paid"].ToString();
lbladt.Text = dr["E_date"].ToString();
//pb_old.Image = (Image)dr["Image_new"];

}
dr.Close();
lbldtr.Text = rec.ToString();
}
}

//cn.Close();
}


catch (Exception c)
{
MessageBox.Show(c.Message);
}
cn.Close();
}