private boolean ifExist(String pos, String empl, String strt, String nd){
        boolean flag = false;
        String sql = "select from EmploymentHistory where empNo=? and jobTitle=? and employer=? and start=? and end=?";
            try{
                conn = DBConnect.connect();
                pst = conn.prepareStatement(sql);
                pst.setString(1, empNm);
                pst.setString(2, pos);
                pst.setString(3, empl);
                pst.setString(4, strt);
                pst.setString(5, nd);
                rs = pst.executeQuery();
                
                if(rs==null){
                    flag=true;
                }
            }
            catch(Exception e){
                JOptionPane.showMessageDialog(null, e);
            }
            finally{
                if(pst != null){
                     try{
                         pst.close();
                    }
                    catch(SQLException e){

                    }
                }
                if(rs != null){
                     try{
                         rs.close();
                    }
                    catch(SQLException e){

                    }
                }
                if(conn != null){
                     try{
                         conn.close();
                    }
                    catch(SQLException e){

                    }
                }
            }
        return flag;
    }