Oracle数据库日期格式转换
select sysdate from dual; select to_char(sysdate,'yyyy/mm/dd hh24:mi:ss') as mydate from dual; select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') as mydate from dual; select to_number(to_char(sysdate,'yyyymmddhh24miss')) as mydate from dual; 转换函数
与date操作关系最大的就是两个转换函数:to_date(),to_char()
to_date():作用将字符类型按一定格式转化为日期类型。 具体用法:to_date('2004-11-27','yyyy-mm-dd'),前者为字符串,后者为转换日期格式。【注意,前后两者要以一对应】
如;to_date('2004-11-27 13:34:43', 'yyyy-mm-dd hh24:mi:ss')
多种日期格式:
YYYY:四位表示的年份 YYY,YY,Y:年份的最后三位、两位或一位,缺省为当前世纪 MM:01~12的月份编号 MONTH:九个字符表示的月份,右边用空格填补 MON:三位字符的月份缩写 WW:一年中的星期 D:星期中的第几天 DD:月份中的第几天 DDD:年所中的第几天 DAY:九个字符表示的天的全称,右边用空格补齐 HH,HH12:一天中的第几个小时,12进制表示法 HH24:一天中的第几个小时,取值为00~23 MI:一小时中的分钟 SS:一分钟中的秒 SSSS:从午夜开始过去的秒数 to_char():将日期转按一定格式换成字符类型 即把当前时间按yyyy-mm-dd hh24:mi:ss格式转换成字符类型 在oracle中处理日期大全 TO_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 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 .... 日期和时间函数汇总 1.日期和字符转换函数用法(to_date,to_char)
select to_char(to_date(222,'J'),'Jsp') from dual; --Two Hundred Twenty-Two 2.求某天是星期几
select to_char(to_date('2018-01-09','yyyy-mm-dd'),'day') from dual; --星期二 select to_char(to_date('2018-01-09','yyyy-mm-dd'),'day','NLS_DATE_LANGUAGE = American') from dual; --tuesday 设置日期语言ALTER SESSION SET NLS_DATE_LANGUAGE='AMERICAN';
也可以这样 TO_DATE ('2002-08-26', 'YYYY-mm-dd', 'NLS_DATE_LANGUAGE = American') 3.两日期间的天数
select floor(sysdate - to_date('19921123','yyyymmdd')) from dual; --9179 select p.claimno, p.endcasedate from prplclaim p UNION select '1', TO_DATE(null) from dual; 注意要用TO_DATE(null)
5.取日期范围
a_date between to_date('20011201','yyyymmdd') and to_date('20011231','yyyymmdd') 6. 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 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 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).
8.时间间隔
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 9.获得小时数
select sysdate ,to_char(sysdate,'hh') from dual; select sysdate ,to_char(sysdate,'hh24') from dual; 10.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; select add_months(trunc(sysdate,'year'), 12) - trunc(sysdate,'year') from dual; to_char( last_day( to_date('02' || :year,'mmyyyy') ), 'dd' ) --如果是28就不是闰年 select to_char(NEW_TIME( sysdate, 'GMT','EST'), 'dd/mm/yyyy hh:mi:ss') ,sysdate from dual; 13.5秒钟一个间隔
select TO_DATE(FLOOR(TO_CHAR(sysdate,'SSSSS')/300) * 300,'SSSSS') ,TO_CHAR(sysdate,'SSSSS')from dual; --SSSSS表示5位秒数 14.一年的第几天
select TO_CHAR(SYSDATE,'DDD'),sysdate from dual; select Days, A, TRUNC(A*24) Hours, 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); floor((date2-date1, 365) /30) 作为月 mod(mod(date2-date1, 365), 30)作为日. 关于日期的函数
在oracle中有很多关于日期的函数,如: 1、add_months()用于从一个日期值增加或减少一些月份 date_value:=add_months(date_value,number_of_months) 例: select add_months(sysdate,12) 'Next Year' from dual; date_value:=current_date select sessiontimezone,current_date from dual; timestamp_with_time_zone_value:=current_timestamp([timestamp_precision]) select sessiontimezone,current_timestamp from dual; select dbtimezone from dual; select extract(month from sysdate) 'This Month' from dual; select extract(year from add_months(sysdate,36)) '3 Years Out' from dual; date_value:=last_day(date_value) select last_day(date'2000-02-01') 'Leap Yr?' from dual; select last_day(sysdate) 'Last day of this month' from dual; select localtimestamp,current_timestamp from dual; select months_between(sysdate,date'1971-05-18') from dual; 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 日 一 二 三 四 五 六 10、周相隔日期函数 trunc() 1.查询某周的第一天 select trunc(decode(ww, 53, to_date(yy || '3112', 'yyyyddmm'), to_date(yy || '-' || to_char(ww * 7), 'yyyy-ddd')), 'd') last_day from (select substr('2004-32', 1, 4) yy, to_number(substr('2004-32', 6)) ww from dual); select trunc(to_date(substr('2003-01',1,5)||to_char((to_number(substr('2003-01',6)))*7),'yyyy-ddd'),'d')-6 first_day from dual; select min(v_date) from (select (to_date('200201','yyyymm') + rownum) v_date from all_tables where rownum < 370) where to_char(v_date,'yyyy-iw') = '2002-49'; select trunc(decode(ww, 53, to_date(yy || '3112', 'yyyyddmm'), to_date(yy || '-' || to_char(ww * 7), 'yyyy-ddd')), 'd') - 6 first_day from (select substr('2004-33', 1, 4) yy, to_number(substr('2004-33', 6)) ww from dual); select trunc(to_date(substr('2003-01',1,5)||to_char((to_number(substr('2003-01',6)))*7),'yyyy-ddd'),'d') last_day from dual; select max(v_date) from (select (to_date('200408','yyyymm') + rownum) v_date from all_tables where rownum < 370) where to_char(v_date,'yyyy-iw') = '2004-33'; select min_date, to_char(min_date,'day') day from (select to_date(substr('2004-33',1,4)||'001'+rownum-1,'yyyyddd') min_date from all_tables where rownum <= decode(mod(to_number(substr('2004-33',1,4)),4),0,366,365) union select to_date(substr('2004-33',1,4)-1|| decode(mod(to_number(substr('2004-33',1,4))-1,4),0,359,358)+rownum,'yyyyddd') min_date from all_tables where rownum <= 7 union select to_date(substr('2004-33',1,4)+1||'001'+rownum-1,'yyyyddd') min_date from all_tables where rownum <= 7 ) where to_char(min_date,'yyyy-iw') ='2004-33'; |
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