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 24小時格式下時間範圍為: 0:00:00 - 23:59:59.... 12小時格式下時間範圍為: 1:00:00 - 12:59:59 .... 1.日期和字元轉換函式用法(to_date,to_char) 2.select to_char( to_date(222,'J'),'Jsp') from dual 顯示Two Hundred Twenty-Two 3.求某天是星期幾 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 設定日期語言 ALTER SESSION SET NLS_DATE_LANGUAGE='AMERICAN'; 也可以這樣 TO_DATE ('2002-08-26', 'YYYY-mm-dd', 'NLS_DATE_LANGUAGE = American') 網管聯盟bitsCN@com 4.兩個日期間的天數 select floor(sysdate - to_date('20020405','yyyymmdd')) from dual; 5. 時間為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') 那麼12月31號中午12點之後和12月1號的12點之前是不包含在這個範圍之內的。 所以，當時間需要精確的時候，覺得to_char還是必要的 7. 日期格式衝突問題 輸入的格式要看你安裝的ORACLE字元集的類型, 比如: US7ASCII, date格式的類型就是: '01-Jan-01' alter system set NLS_DATE_LANGUAGE = American alter session set NLS_DATE_LANGUAGE = American 或者在to_date中寫 select to_char(to_date('2002-08-26','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = American') from dual; 注意我這隻是舉了NLS_DATE_LANGUAGE，當然還有很多， 可查看 select * from nls_session_parameters select * from V$NLS_PARAMETERS 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' ) 尋找2002-02-28至2002-02-01間除星期一和七的天數 在前後分別調用DBMS_UTILITY.GET_TIME, 讓後將結果相減(得到的是1/100秒, 而不是毫秒). select months_between(to_date('01-31-1999','MM-DD-YYYY'), to_date('12-31-1998','MM-DD-YYYY')) "MONTHS" FROM DUAL; 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:第一條記錄的TIME 與最後一行是一樣的 可以建立一個函數來處理這個問題 create or replace function sys_date return date is begin return sysdate; end; select to_char(sys_date,'hh:mi:ss') from all_objects; 網管u家u.bitsCN.com 12.獲得小時數 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; SYSDATE TO_CHAR(SYSDATE,'HH24') -------------------- ----------------------- 2003-10-13 19:35:21 19 擷取年月日與此類似 13.年月日的處理 select older_date, newer_date, years, months, abs( trunc( newer_date- add_months( older_date,years*12+months ) ) ) 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 ) ) 14.處理月份天數不定的辦法 select to_char(add_months(last_day(sysdate) +1, -2), 'yyyymmdd'),last_day(sysdate) from dual 15.找出今年的天數 select add_months(trunc(sysdate,'year'), 12) - trunc(sysdate,'year') from dual 閏年的處理方法 to_char( last_day( to_date('02' || :year,'mmyyyy') ), 'dd' )
