當同時查詢多個數據集合時，需要定義多個statement，因為每個若同時使用一個statement，那麼資料會不斷進行覆蓋。

while(rs.next()) {
                cnt++;
                String provinceid = rs.getString("provinceId");
                String provinceName = rs.getString("provinceName");
                String sql2 = "select * from tcity where provinceId="
 
+provinceid;
                ResultSet rs2 = stat2.executeQuery(sql2);
                out.println("<tr>");
                out.println("<th colspan = \"2\" id = \"firstrow\">"+provinceName+"</th>");
                out.println("</tr>");
                out.println("<tr>"
 
);
                out.println("<th>郵政編碼</th>");
                out.println("<th>城市名稱</th>");
                out.println("</tr>");
                while(rs2.next()) {
                    String cityName = rs2.getString("cityName");
                    String cityCode = rs2.
 
getString("cityCode");
                    out.println("<tr>");
                    out.println("<th>"+cityCode+"</th>");
                    out.println("<th>"+cityName+"</th>");
                    out.println("</tr>");
                  //  out.print(provinceName+" "+city);
                  //  out.print("<br>");
                }

            }
        out.println("</table>");