oracle 日期常用函數 (SYSDATE、日期格式)

 SYSDATE                                                                              

--◎ 可得到目前系統的時間                                                            

                                                                                     

  ex.                                                                                

    select sysdate from dual;                                                        

                                                                                     

    sysdate                                                                          

    ----------                                                                       

    20-SEP-07                                                                        

                                                                                     

 常用之日期格式                                                                      

                                                                                     

 日期格式                 說明                                                       

 ------------------------------------------------------------------------            

 YYYY/MM/DD              -- 年/月/日                                                 

 YYYY                    -- 年(4位)                                                  

 YYY                     -- 年(3位)                                                  

 YY                      -- 年(2位)                                                  

 MM                      -- 月份                                                     

 DD                      -- 日期                                                     

 D                       -- 星期                                                     

                             -- 星期日 = 1  星期一 = 2 星期二 = 3                    

                         -- 星期三 = 4  星期四 = 5 星期五 = 6 星期六 = 7             

                                                                                     

 DDD                     -- 一年之第幾天                                             

 WW                      -- 一年之第幾週                                             

 W                       -- 一月之第幾週                                             

 YYYY/MM/DD HH24:MI:SS   -- 年/月/日 時(24小時制):分:秒                              

 YYYY/MM/DD HH:MI:SS     -- 年/月/日 時(非24小時制):分:秒                            

 J                       -- Julian day，Bc 4712/01/01 為1                            

 RR/MM/DD                -- 公元2000問題                                             

    　　　　　　　　　　　　-- 00-49 = 下世紀；50-99 = 本世紀                        

 ex.        

select to_char(sysdate,'YYYY/MM/DD') FROM DUAL;             -- 2007/09/20
select to_char(sysdate,'YYYY') FROM DUAL;                   -- 2007
select to_char(sysdate,'YYY') FROM DUAL;                    -- 007
select to_char(sysdate,'YY') FROM DUAL;                     -- 07
select to_char(sysdate,'MM') FROM DUAL;                     -- 09
select to_char(sysdate,'DD') FROM DUAL;                     -- 20
select to_char(sysdate,'D') FROM DUAL;                      -- 5
select to_char(sysdate,'DDD') FROM DUAL;                    -- 263
select to_char(sysdate,'WW') FROM DUAL;                     -- 38
select to_char(sysdate,'W') FROM DUAL;                      -- 3
select to_char(sysdate,'YYYY/MM/DD HH24:MI:SS') FROM DUAL;  -- 2007/09/20 15:24:13
select to_char(sysdate,'YYYY/MM/DD HH:MI:SS') FROM DUAL;    -- 2007/09/20 03:25:23
select to_char(sysdate,'J') FROM DUAL;                      -- 2454364
select to_char(sysdate,'RR/MM/DD') FROM DUAL;               -- 07/09/20