oracle日期处理完整版-阿里云开发者社区

O_DATE格式
   Day:
   dd       number         12
   dy       abbreviated    fri
   day      spelled out    friday
   ddspth   spelled out,   ordinal   twelfth
   Month:
   mm       number         03
   mon      abbreviated    mar
   month    spelled out    march
   Year:
   yy       two digits    98
   yyyy     four digits   1998

字串2

   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 ....
1.
   日期和字符转换函数用法（to_date,to_char）

2.
   select to_char( to_date(222,'J'),'Jsp') from dual

   显示Two Hundred Twenty-Two

3.
   求某天是星期几
   select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day') from dual;
   星期一
   select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = American') from dual;
   monday
   设置日期语言
   ALTER SESSION SET NLS_DATE_LANGUAGE='AMERICAN';
   也可以这样
字串9
   TO_DATE ('2002-08-26', 'YYYY-mm-dd', 'NLS_DATE_LANGUAGE = American')

4.
   两个日期间的天数
   select floor(sysdate - to_date('20020405','yyyymmdd')) from dual;

5.     时间为null的用法
   select id, active_date from table1
     UNION
   select 1, TO_DATE(null) from dual;

   注意要用TO_DATE(null)

6.
   a_date between to_date('20011201','yyyymmdd') and to_date('20011231','yyyymmdd')
   那么12月31号中午12点之后和12月1号的12点之前是不包含在这个范围之内的。
   所以，当时间需要精确的时候，觉得to_char还是必要的
7.      日期格式冲突问题
         输入的格式要看你安装的ORACLE字符集的类型, 比如: US7ASCII, date格式的类型就是: '01-Jan-01'
   alter system set NLS_DATE_LANGUAGE = American 字串3

         alter session set NLS_DATE_LANGUAGE = American
   或者在to_date中写
   select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = American') from dual;
   注意我这只是举了NLS_DATE_LANGUAGE，当然还有很多，
   可查看
   select * from nls_session_parameters
   select * from V$NLS_PARAMETERS

日期和字符转换函数用法（to_date,to_char）
         We overwrite NLS_DATE_FORMAT into different formats for the session.
         SQL> alter session set nls_date_format = 'DD-MON-RR'; Session altered.
         SQL> set pagesize 0
     SQL> set linesize 130
     SQL> select * from nls_session_parameters;
     NLS_LANGUAGE                   AMERICAN 字串6
字串4

     NLS_TERRITORY                  AMERICA
     NLS_CURRENCY                   $
     NLS_ISO_CURRENCY               AMERICA
     NLS_NUMERIC_CHARACTERS         .,
     NLS_CALENDAR                   GREGORIAN
     NLS_DATE_FORMAT                DD-MON-RR
     NLS_DATE_LANGUAGE              AMERICAN
     NLS_SORT                       BINARY
     NLS_TIME_FORMAT                HH.MI.SSXFF AM 字串1
字串1

     NLS_TIMESTAMP_FORMAT           DD-MON-RR HH.MI.SSXFF AM
     NLS_TIME_TZ_FORMAT             HH.MI.SSXFF AM TZH:TZM
     NLS_TIMESTAMP_TZ_FORMAT        DD-MON-RR HH.MI.SSXFF AM TZH:TZM
     NLS_DUAL_CURRENCY              $
     NLS_COMP                       BINARY

     15 rows selected.
          specify it in SQL statement:

        SQL> select to_date('03-SEP-1999','DD-MON-YYYY') from dual;
         03-SEP-99
        SQL> alter session set nls_date_format = 'MM-DD-YYYY';
             Session altered.
字串6

        SQL> select to_date('03-SEP-99','DD-MON-YY') from dual;
             TO_DATE('0
             ----------
             09-03-1999
        SQL> alter session set nls_date_format = 'RRRR-MM-DD';
             Session altered.

        SQL> select to_date('03-SEP-1999','DD-MON-YYYY') from dual;
             TO_DATE('0
             ----------
             1999-09-03
    When we use TO_CHAR function, we get expected results of format from current SQL statement:   字串9
        SQL> alter session set nls_date_format = 'MM-DD-YY';
             Session altered.
        SQL> select to_char(sysdate,'dd-mm-yyyy') from dual;
             TO_CHAR(SYSDATE,'DD-MM-YYYY')
             07-09-1999
        SQL> alter session set nls_date_format = 'RR-MON-DD';
             Session altered.
        SQL> select to_char(sysdate,'dd-mon-yy') from dual;
             TO_CHAR(SYSDATE,'DD-MON-YY')
             07-sep-99   字串7
        SQL> select to_char(sysdate,'dd-Mon-yy') from dual;
             TO_CHAR(SYSDATE,'DD-MON-YY')   字串1
             07-Sep-99
8.
   select count(*)
   from ( select rownum-1 rnum
          from all_objects
          where rownum <= to_date('2002-02-28','yyyy-mm-dd') - to_date('2002-
          02-01','yyyy-mm-dd')+1
         )
   where to_char( to_date('2002-02-01','yyyy-mm-dd')+rnum-1, 'D' )
   not
   in ( '1', '7' )

   查找2002-02-28至2002-02-01间除星期一和七的天数
   在前后分别调用DBMS_UTILITY.GET_TIME, 让后将结果相减(得到的是1/100秒, 而不是毫秒).

9.
   select months_between(to_date('01-31-1999','MM-DD-YYYY'),
     to_date('12-31-1998','MM-DD-YYYY')) "MONTHS" FROM DUAL;
字串4

   1

   select months_between(to_date('02-01-1999','MM-DD-YYYY'),
     to_date('12-31-1998','MM-DD-YYYY')) "MONTHS" FROM DUAL;

   1.03225806451613
10.     Next_day的用法
   Next_day(date, day)

   Monday-Sunday, for format code DAY
   Mon-Sun, for format code DY
   1-7, for format code D

11
   select to_char(sysdate,'hh:mi:ss') TIME from all_objects
   注意：第一条记录的TIME 与最后一行是一样的

   可以建立一个函数来处理这个问题
   create or replace function sys_date return date is
   begin
   return sysdate;   字串5
   end;

   select to_char(sys_date,'hh:mi:ss') from all_objects;
12.
         获得小时数

         SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 2:38:40') from offer
         SQL>   select sysdate ,to_char(sysdate,'hh') from dual;

         SYSDATE              TO_CHAR(SYSDATE,'HH')
         -------------------- ---------------------
         2003-10-13 19:35:21 07

         SQL>   select sysdate ,to_char(sysdate,'hh24') from dual; 字串8

         SYSDATE              TO_CHAR(SYSDATE,'HH24')
         -------------------- -----------------------
         2003-10-13 19:35:21 19

         获取年月日与此类似
13.
   年月日的处理
   select older_date,
            newer_date,
            years,
            months,
            abs(
              trunc(
                 newer_date-
                     add_months( older_date,years*12+months )

字串6

                   )
              ) days
      from ( select
         trunc(months_between( newer_date, older_date )/12) YEARS,
       mod(trunc(months_between( newer_date, older_date )),
             12 ) MONTHS,
                    newer_date,
                    older_date
               from ( select hiredate older_date,
                  add_months(hiredate,rownum)+rownum newer_date
                        from emp ) 字串3
           )

14.
   处理月份天数不定的办法
   select to_char(add_months(last_day(sysdate) +1, -2), 'yyyymmdd'),last_day(sysdate) from dual

16.
   找出今年的天数
   select add_months(trunc(sysdate,'year'), 12) - trunc(sysdate,'year') from dual

   闰年的处理方法
   to_char( last_day( to_date('02' || :year,'mmyyyy') ), 'dd' )
   如果是28就不是闰年

17.
   yyyy与rrrr的区别
   'YYYY99 TO_C
   ------- ----
   yyyy 99 0099
   rrrr 99 1999
   yyyy 01 0001
字串2
   rrrr 01 2001

18.不同时区的处理
   select to_char( NEW_TIME( sysdate, 'GMT','EST'), 'dd/mm/yyyy hh:mi:ss') ,sysdate
   from dual;

19.
   5秒钟一个间隔
   Select TO_DATE(FLOOR(TO_CHAR(sysdate,'SSSSS')/300) * 300,'SSSSS') ,TO_CHAR(sysdate,'SSSSS')
    from dual

    2002-11-1 9:55:00 35786
    SSSSS表示5位秒数

20.
   一年的第几天
   select TO_CHAR(SYSDATE,'DDD'),sysdate from dual
   310 2002-11-6 10:03:51

21.计算小时,分,秒,毫秒
   select
           Days,
           A,
           TRUNC(A*24)                                     Hours, 字串2

字串7

           TRUNC(A*24*60 - 60*TRUNC(A*24))                 Minutes,
           TRUNC(A*24*60*60 - 60*TRUNC(A*24*60))           Seconds,
           TRUNC(A*24*60*60*100 - 100*TRUNC(A*24*60*60))   mSeconds
   from
   (
   select
           trunc(sysdate)             Days,
           sysdate - trunc(sysdate)      A
   from dual
   )


9i以上版本
    -----------------------------
    SQL>select to_char(systimestamp,'yyyy-mm-dd hh24:mi:ssxff') time1,
    to_char(current_timestamp) time2 from dual;      字串3
    TIME1                         TIME2
    ----------------------------- ----------------------------------------------------------------
    2003-10-24 10:48:45.656000    24-OCT-03 10.48.45.656000 AM +08:00
    可以看到，毫秒在to_char中对应的是FF。

    SQL> select to_timestamp('2003-10-24 10:48:45.656000','yyyy-mm-dd hh24:mi:ssxff') from dual;

    TO_TIMESTAMP('2003-10-2410:48:
    -------------------------------------------------
    24-10月-03 10.48.45.656000000 上午

22.
floor((date2-date1) /365) 作为年
floor((date2-date1, 365) /30) 作为月
mod(mod(date2-date1, 365), 30)作为日.
23.next_day函数
next_day(sysdate,6)是从当前开始下一个星期五。后面的数字是从星期日开始算起。
1 2 3 4 5 6 7
字串2

日一二三四五六

24.取出一个时间段中星期日星期六的天数
function weekends( p_date1 in date, p_date2 in date )
return number
as
     l_date1 date default least(p_date1,p_date2);
     l_date2 date default greatest(p_date1,p_date2);
     l_days number default trunc(l_date2-l_date1)+1;
     l_cnt   number;
begin
     select count(*) into l_cnt
       from (select rownum r
               from all_objects where rownum <= l_days)
      where to_char(l_date1+r-1,'dy') in ( 'sat','sun' );

     return l_cnt;
end;

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分类: Oracle

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