一.根据更新时间排序
1.插入
insert into t_user t (t.user_id,t.user_name,t.create_time,t.update_time)values('10','11',sysdate,sysdate);
2.更新
update T_USER t set t.update_time = sysdate where t.user_id='7'
update T_USER t set t.update_time = sysdate where t.user_id='9'
3.排序
select t.*, t.rowid from T_USER t order by t.update_time desc
二.oracle 查询时给某个字段一个默认值
select nvl(columnName,'0') name from tableName;