oracle 查询本周，本月，本年

 --本周
select * from dual where time > sysdate - (to_char(sysdate-1,'D'))
--本月
select * from dual where time>=TRUNC(SYSDATE, 'MM') and time<=last_day(SYSDATE)
--本年
select * from dual where to_char(time,'yyyy')=to_char(sysdate,'yyyy')