Database insert error: "string or binary data would be truncated"

When I log in, I am storing my username in the session. My requirement is that I want to store my username in my database. Here I am storing it in username1. When the username is entered, I can print it using response.write() and it is printing perfectly. However, when I am storing it in the database it is producing this error:

**sqlException was unhandled by user code
and exception at       cmd.ExecuteScalar();
String or binary data would be truncated.
The statement has been terminated.**

Following is my ado.net code:

using (SqlConnection con = 
    new SqlConnection("Data Source=.;database=testdb1;Integrated Security=SSPI")) {

    con.Open();
    //  SqlCommand cmd = new SqlCommand("delete from fileinfo where ID=" + Convert.ToInt32(Request.Params["one"]), con);                            

    string uname = (string) Session["fname"].ToString() + " " + Session["lname"].ToString(); //Session["fname"].ToString()+" "+Session["lname"].ToString();

    // Response.Write(uname);
    // uname = "sri hari";
    uname = uname + " ";
    string uname1 = uname;
    uname = uname.Trim();
    SqlCommand cmd = new SqlCommand("insert into qry_details values('" + txt_query_name.Text + "','pending for approval','" + txt_query_description.Text + "','" + DateTime.Now.ToString("yyyy-MM-dd") + "','" + qry + "','" + uname1 + "')", con);
    cmd.ExecuteScalar();
}