关于group by的一段SQl语句——Oracle

select cc.fformulacode, cc.rangedate, dd.fpervalue
  from (select n1.fformulacode, max(n1.frangedate) as rangedate
          from table1 n1
         where n1.frangedate <= to_date('2012-10-17', 'yyyy-MM-dd')
         group by n1.fformulacode) cc
  left join table1 dd
    on cc.fformulacode = dd.fformulacode
   and cc.rangedate = dd.frangedate

tb_001_Para_Performula_Rela 建表语句如下：（应该考虑主键）

create table Table1
(
  FFORMULACODE VARCHAR2(20) not null,
  FRANGEDATE   DATE not null,
  FRANGEMONEY  NUMBER(18,4) not null,
  FPERTYPE     NUMBER(1) not null,
  FPERVALUE    NUMBER(18,12) not null,
  FFIXVALUE    NUMBER(18,4) not null,
  FLEASTVALUE  NUMBER(18,4) not null,
  FMAXVALUE    NUMBER(18,4) default 0 not null,
  FCHECKSTATE  NUMBER(1) not null,
  FCREATOR     VARCHAR2(20) not null,
  FCREATETIME  VARCHAR2(20) not null,
  FCHECKUSER   VARCHAR2(20),
  FCHECKTIME   VARCHAR2(20)
)