Oracle11g: datetime

--上一月，上一年
select add_months(sysdate,-1) last_month,add_months(sysdate,-12) last_year from dual;

--下一月，下一年
select add_months(sysdate,1) last_month,add_months(sysdate,12) last_year from dual;

--当月最后一天

select last_day(sysdate) from dual;

--下周日期

select next_day(sysdate,'星期五') "下周五" from dual;
select next_day(sysdate, 'friday') "next friday" from dual;
select next_day(sysdate, 4) from dual;

--固定日期一天
select * from account a where a.applytime>= to_date('2011-02-26','yyyy-mm-dd') and a.applytime< to_date('2011-02-27','yyyy-mm-dd');
--前天一天
select * from account a where a.applytime>= to_date(to_char(sysdate-2,'yyyy-mm-dd'),'yyyy-mm-dd') and a.applytime< to_date(to_char(sysdate-1,'yyyy-mm-dd'),'yyyy-mm-dd');
-- 昨天一天
select * from dxw_tmp a where a.applytime>= to_date(to_char(sysdate-1,'yyyy-mm-dd'),'yyyy-mm-dd') and a.applytime< to_date(to_char(sysdate,'yyyy-mm-dd'),'yyyy-mm-dd');
--今天一天
select * from account a where a.applytime>= to_date(to_char(sysdate,'yyyy-mm-dd'),'yyyy-mm-dd') and a.applytime< to_date(to_char(sysdate+1,'yyyy-mm-dd'),'yyyy-mm-dd');

-- 上月第一天
select to_date(to_char(add_months(sysdate,-2)+1,'yyyy-mm-dd'),'yyyy-mm-dd') from dual ;
-- 上月最后一天
select to_date(to_char(add_months(sysdate,-1),'yyyy-mm-dd'),'yyyy-mm-dd') from dual;

select * from account a where a.applytime>= to_date(to_char(add_months(sysdate,-2)+1,'yyyy-mm-dd'),'yyyy-mm-dd') and a.applytime<= to_date(to_char(add_months(sysdate,-1),'yyyy-mm-dd'),'yyyy-mm-dd');

select to_date(to_char(add_months(sysdate,-2),'yyyy-mm-dd'),'yyyy-mm-dd') from dual;
select to_date(to_char(add_months(sysdate,-3)+1,'yyyy-mm-dd'),'yyyy-mm-dd') from dual ;


 --trunc 截取日期

--当天零点

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

--当月一号

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

--本年一月一号

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

--当前毫秒级时间 6位

select to_char(current_timestamp,'yyyy-mm-dd hh24:mi:ss.ff6') from dual;


--字符串转为 timestamp类型

select to_timestamp('2012-02-03 10:29:46.453234','yyyy-mm-dd hh24:mi:ss.ff6') from dual;

--timestamp转为字符型

select to_char(systimestamp,'yyyy-mm-dd hh24:mi:ss.ff6') from dual;

select cast(sysdate as timestamp) from dual;

select to_char(sysdate,'yyyymmdd w hh24:mi:ss') from dual; 
select to_char(sysdate,'yyyymmdd ww hh24:mi:ss') from dual; 

select to_char(sysdate,'yyyymmdd ww hh24:mi:ss') from dual; 

select to_char(systimestamp,'yyyymmdd ww hh24:mi:ss.ff6') from dual;


-- 月第几周
select to_char(sysdate,'yyyy-mm-dd w hh24:mi:ss') from dual; 
-- 年第几周
select to_char(sysdate,'yyyy-mm-dd ww hh24:mi:ss') from dual; 

-- 第几季度  ff6 date 没有6位的秒位
select to_char(sysdate,'yyyy-mm-dd q ww hh24:mi:ss') from dual;

select to_char(systimestamp,'yyyy-mm-dd q ww hh24:mi:ss.ff6') from dual;

select to_char(sysdate,'sssss') from dual;


/*
o_date格式(以时间:2007-11-02   13:45:25为例)
   
        year:      
        yy two digits 两位年                显示值:07
        yyy three digits 三位年                显示值:007
        yyyy four digits 四位年                显示值:2007
            
        month:      
        mm    number     两位月              显示值:11
        mon    abbreviated 字符集表示          显示值:11月,若是英文版,显示nov     
        month spelled out 字符集表示          显示值:11月,若是英文版,显示november 
          
        day:      
        dd    number         当月第几天        显示值:02
        ddd    number         当年第几天        显示值:02
        dy    abbreviated 当周第几天简写    显示值:星期五,若是英文版,显示fri
        day    spelled out   当周第几天全写    显示值:星期五,若是英文版,显示friday        
        ddspth spelled out, ordinal twelfth 
             
              hour:
              hh    two digits 12小时进制            显示值:01
              hh24 two digits 24小时进制            显示值:13
              
              minute:
              mi    two digits 60进制                显示值:45
              
              second:
              ss    two digits 60进制                显示值:25
              
              其它
              q     digit         季度                  显示值:4
              ww    digit         当年第几周            显示值:44
              w    digit          当月第几周            显示值:1
              
        24小时格式下时间范围为： 0:00:00 - 23:59:59....      
        12小时格式下时间范围为： 1:00:00 - 12:59:59 .... 
*/

 
select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))/365) as spanyears from dual        --时间差-年

select ceil(months_between(sysdate,to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))) as spanmonths from dual        --时间差-月
select months_between('19-12月-1999','19-3月-1999') mon_between from dual; 
select months_between(to_date('2000.05.20','yyyy.mm.dd'),to_date('2005.05.20','yyyy.mm.dd')) mon_betw from dual;

select (extract(year from to_date('2009-05-01','yyyy-mm-dd')) - extract(year from to_date('2008-04-30','yyyy-mm-dd'))) * 12 + 
       extract(month from to_date('2008-05-01','yyyy-mm-dd')) - extract(month from to_date('2008-04-30','yyyy-mm-dd')) months 
from dual; 

select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))) as spandays from dual             --时间差-天
select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))*24) as spanhours from dual         --时间差-时
select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))*24*60) as spanminutes from dual    --时间差-分
select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))*24*60*60) as spanseconds from dual --时间差-秒

select ceil((to_date('2008-05-02 00:00:00' , 'yyyy-mm-dd hh24-mi-ss') - to_date('2008-04-30 23:59:59' , 'yyyy-mm-dd hh24-mi-ss')) * 24 * 60 * 60 * 1000) 相差豪秒数 from dual; 
select ceil((to_date('2018-05-02 00:00:00' , 'yyyy-mm-dd hh24-mi-ss') - to_date('2018-04-30 23:59:59' , 'yyyy-mm-dd hh24-mi-ss')) * 24 * 60 * 60) 相差秒数 from dual; 

--加1年
select sysdate,add_months(sysdate,12) from dual; 
  
--加1月 
select sysdate,add_months(sysdate,1) from dual;   
--加1星期 
select sysdate,to_char(sysdate+7,'yyyy-mm-dd hh24:mi:ss') from dual; 
--加1天 
select sysdate,to_char(sysdate+1,'yyyy-mm-dd hh24:mi:ss') from dual; 
--加1小时   
select sysdate,to_char(sysdate+1/24,'yyyy-mm-dd hh24:mi:ss') from dual; 
 --加1分钟  
select sysdate,to_char(sysdate+1/24/60,'yyyy-mm-dd hh24:mi:ss') from dual; 
--加1秒 
select sysdate,to_char(sysdate+1/24/60/60,'yyyy-mm-dd hh24:mi:ss') from dual;  
--加7天
select   sysdate+7   from   dual;    

-- https://docs.oracle.com/cd/e11882_01/server.112/e10729/ch4datetime.htm#nlspg256

declare 
ddate timestamp;
sdate date;
begin
  ddate:= systimestamp;
  sdate:=sysdate;
dbms_output.put_line(ddate);
dbms_output.put_line(sdate);
end;