How you are saving the data in to table.
There might be more than one value will be available in your!!!!!
Are you selecting only last inserted value then use ExecuteScalar function.
Set the value like this
con.Open();
string day = cmd.ExecuteScalar().ToString();
con.Close();
if (ddlDays.Items.FindByText(day) != null)
{
ddlDays.Items.FindByText(day).Selected = true;
}