From Evernote:

ORACLE 开始时间 & 结束时间 Clipped from: http://blog.csdn.net/long_ge_cool/article/details/8601157

SELECT to_date(to_char(sysdate+1,'yyyy-mm-dd'),'yyyy-mm-dd') from dual 今天结束时间

SELECT to_date(to_char(sysdate,'yyyy-mm-dd'),'yyyy-mm-dd') from dual 今天开始时间

获取上一个小时的开始时间和结束时间 
select to_date(to_char(sysdate,'yyyy-mm-dd')||(to_char(sysdate,'hh24')-1),'yyyy-mm-dd hh24') from dual; 
select to_date(to_char(sysdate,'yyyy-mm-dd')||(to_char(sysdate,'hh24')),'yyyy-mm-dd hh24') from dual;

-- 获取上月的开始时间和结束时间 
select to_char(to_date(to_char(add_months(sysdate,-1),'yyyy-mm'),'yyyy-mm'),'yyyy-mm-dd hh24:mi:ss') from dual; 
select to_char(to_date(to_char(sysdate,'yyyy-mm'),'yyyy-mm'),'yyyy-mm-dd hh24:mi:ss') from dual; 

--本周 

select trunc(sysdate,'d')+1 from dual; 

select trunc(sysdate,'d')+7 from dual; 

--本月 

select trunc(sysdate,'mm') from dual; 

select last_day(trunc(sysdate)) from dual; 

--本季 

select trunc(sysdate,'Q') from dual; 

select add_months(trunc(sysdate,'Q'),3)-1 from dual; 

--本年 

select trunc(sysdate,'yyyy') from dual; 

select add_months(trunc(sysdate,'yyyy'),12)-1 from dual;