oracle的伪列与分页

1.《oralce菜鸟1000问》导读，属性系统信息查询
2.rowid 和 rownum

3.使用伪列删除重复数据

select rownum,rowid,USRID,GRPID,UNAME,SAL,BRITH from ORA1.T_USER a
 where a.rowid !=
 (
  select max(b.rowid) from  ORA1.T_USER b where  a.GRPID = b.GRPID and a.UNAME = b.UNAME
 )
;

4.分页查询
--第一种，按照rowid+rownum来分
select * from T_USER where rowid in
 (select rid from 
     (select rid,rownum as  rn from 
         ( select rowid rid from T_USER)
           where rownum<=50 )
      where rn>=10) 
order by usrid;

select * from T_USER where rownum<=9
  minus
select * from T_USER where rownum<=6;

select * from 
      (select a.*,row_number() over(order by usrid) as rn from T_USER a)
  where rn>=4 and rn<=6;