orale取日期差以及转换日期

select  inception_date ,to_date(to_char(sysdate-1,'yyyymmdd'),'yyyymmdd') yesd ,
case when to_date(to_char(sysdate-1,'yyyymmdd'),'yyyymmdd')>planned_end_date
then trunc(planned_end_date - inception_date ) else trunc(sysdate-1 - inception_date ) ,to_char(sysdate,'yyyy') year
end as ss,policy_no,sysdate - 1

from auto_agreement_t where policy_no="xxx"

and themonth= extract(month from to_date('07/31/2009','mm-dd-yyyy'))

;