为什么updateSql不能在while循环中执行？

Question

当我有 select 时，这有效：

public static void main(String[] args){

    try{
            Connection conn = DriverManager.getConnection("jdbc:oracle:XXXXX", "username", "psw");
            Statement stm = conn.createStatement();
            String selectSql="select h.id, h.user_id,h.start_time,h.end_time,h.start_date,h.end_date, a.time_zone from hos_driving_log h left join user_info ua on h.user_id= ua.user_id left JOIN account a on a.acct_id = ua.acct_id";

            ResultSet ress = stm.executeQuery(selectSql);
            while(ress.next()){
                int id = ress.getInt("id");
                String user_id = ress.getString("user_id");
                long start_time = ress.getLong("start_time");
                long end_time = ress.getLong("end_time");
                int start_date = ress.getInt("start_date");
                int end_date = ress.getInt("end_date");
                String time_zone = ress.getString("time_zone");
                System.out.println(id+" "+user_id+" "+start_time+" "+end_time+" "+start_date+" "+end_date+" "+time_zone);
            }
        }catch(SQLException e){
        e.printStackTrace();
        }
    //Close the resources - Done automatically by try-with-resources
}

输出：

1 testuser 20151025021324 20151026024135 0 0 GMT-12:00
2 hostest 20151026024135 20151022080352 0 0 GMT-07:00
24 stress0101 20151208075641 20151208075717 0 0 null
88 123 c 20151224085208 20151224130803 0 0 null
89 123 c 20151224130916 20151224130922 0 0 null
90 123 c 20151224130917 20151224130923 0 0 null
91 123 c 20151224130918 20151224130924 0 0 null
92 123 c 20151224130919 20151224130925 0 0 null

但是当我想在循环中更新时：

try{
        Connection conn = DriverManager.getConnection("jdbc:oracle:XXXXX", "username", "psw");
        Statement stm = conn.createStatement();
        String selectSql="select h.id, h.user_id,h.start_time,h.end_time,h.start_date,h.end_date, a.time_zone from hos_driving_log h left join user_info ua on h.user_id= ua.user_id left JOIN account a on a.acct_id = ua.acct_id";

        ResultSet ress = stm.executeQuery(selectSql);
        while(ress.next()){
            int id = ress.getInt("id");
            String user_id = ress.getString("user_id");
            long start_time = ress.getLong("start_time");
            long end_time = ress.getLong("end_time");
            int start_date = ress.getInt("start_date");
            int end_date = ress.getInt("end_date");
            String time_zone = ress.getString("time_zone");
            System.out.println(id+" "+user_id+" "+start_time+" "+end_time+" "+start_date+" "+end_date+" "+time_zone);
            start_date = getDrivingLogShortTypeDate(start_time, time_zone);
            end_date = getDrivingLogShortTypeDate(end_time, time_zone);
            String updateSql = "update hos_driving_log set start_date = "+ start_date+",end_date = "+end_date+" where id="+id;
            int i = stm.executeUpdate(updateSql);
            System.out.println(updateSql);
        }
    }catch(SQLException e){
    e.printStackTrace();
    }
//Close the resources - Done automatically by try-with-resources

...它只进行一次更新：

45 co2-stress0096 20151222090816 20151222091436 20151222 20151222 GMT+08:00
update hos_driving_log set start_date = 20151222,end_date = 20151222 where id=45

为什么一更新就停了？我怎样才能更新所有的行？

Answer 1

因为当生成它的 Statement 对象关闭、重新执行或用于从多个结果序列中检索下一个结果时，ResultSet 对象会自动关闭。

您正在重新执行生成结果集的语句对象 stm。您需要使用单独的语句对象进行更新。

此外，不要通过将文字连接到 SQL 来构建 SQL 更新语句。使用绑定变量，您的用户和 DBA 都会感谢您。

见https://docs.oracle.com/javase/7/docs/api/java/sql/ResultSet.html

为什么updateSql不能在while循环中执行？

Why can‘t updateSql be excuted in while-loop？

java

sql

oracle

mybatis