好的SQL收集 不断更新中

1.求1..10偶数之和
select sum(level) from dual
where mod(level,2)=0
connect by level
 
2.将update改换成用rowid来实现。
（1）新的写法：
merge into SNAPSHOT120_2010_572 t1
using (select a.rowid rid, b.vip_level, b.manager_name
       from xyf_vip_info_new b, snapshot120_2010_572 a
     where b.sub_id = a.sub_id) t2
on (t1.rowid=t2.rid)
when matched then
   update set t1.vip_level=t2.vip_level, t1.vip_manager=t2.manager_name
when not matched then
   insert (t1.vip_level) values (null);
 
（2）新奇的写法
UPDATE (SELECT a.vip_level, a.vip_manager,b.vip_level AS b_vip_level, b.manager_name
          from snapshot120_2010_572 a,xyf_vip_info_new b
 
       WHERE b.sub_id = a.sub_id
        )
   SET vip_level = b_vip_level,vip_manager=manager_name;
3.求各个分值和总的数目
select decode(grouping(a.com_name),1,'员工总数',a.com_name),count(b.com_id)
from a,b
where a.com_id=b.com_id
group by rollup(a.com_name);
 
4. 回滚数据到特定时间 
select *
from oj_group
as of timestamp to_date(sysdate,'yyyymmdd hh24:mi:ss' )