1、6、greatest(d1,d2,.dn)给出的日期列表中最后的日期selectsysdateasthis_day,greatest(sysdate,sysdate+1,sysdate+2)asmax_day from dual;THIS_DAY MAX_DAY08-9月-10 10-9月-107、least(d1,k2,.dn)给出的日期列表中最早的日期 select sysdate as this_day,least(sysdate,sysdate+1,sysdate-1) as min_dayfrom dual;THIS_DAY MIN_DAY08-9月-10 07-9月-108、to_
2、char(d ,fmt)日期d按fmt指定的格式转变成字符串) as today from dual;TODAY-2010-09-08 10:37:089、to_date(st ,fmt)字符串st按fmt指定的格式转成日期值,若fmt忽略,st要用缺省格式 select to_date(08) as todayfrom dual;-08-9月-1010、round(d ,fmt)日期d按fmt指定格式舍入到最近的日期) as this,round(sysdate) as round_day,to_char(sysdate+1/6,) as next_4hour,round(sysdate+1
3、/6) as round_dayfrom dual;THIS ROUND_DAY NEXT_4HOUR ROUND_DAY- - - -2010-09-08 10:52:45 08-9月-10 2010-09-08 14:45 09-9月-1011、trunc(d ,fmt)日期d按fmt指定格式截断到最近的日期,trunc(sysdate) as trunc_day) as next_4hour,trunc(sysdate+1/6) as trunc_dayTHIS TRUNC_DAY NEXT_4HOUR TRUNC_DAY56:18 08-9月-10 2010-09-08 14:18 0
4、8-9月-10to_date字符串类型转为换日期类型字符串中的相应位置上的字符,必须符合时间范围的限制查询Oracle日期格式-select * from nls_database_parameters;得到结果如下表:表中NLS_DATE_FORMAT表示日期格式.PARAMETER VALUE- -NLS_LANGUAGE AMERICANNLS_TERRITORY AMERICANLS_CURRENCY $NLS_ISO_CURRENCY AMERICANLS_NUMERIC_CHARACTERS .,NLS_CHARACTERSET ZHS16GBKNLS_CALENDAR GREGO
5、RIANNLS_DATE_FORMAT DD-MON-RRNLS_DATE_LANGUAGE AMERICANNLS_SORT BINARYNLS_TIME_FORMAT HH.MI.SSXFF AMNLS_TIMESTAMP_FORMAT DD-MON-RR HH.MI.SSXFF AMNLS_TIME_TZ_FORMAT HH.MI.SSXFF AM TZH:TZMNLS_TIMESTAMP_TZ_FORMAT DD-MON-RR HH.MI.SSXFF AM TZH:NLS_DUAL_CURRENCY $NLS_COMP BINARYNLS_NCHAR_CHARACTERSET ZHS1
6、6GBKNLS_RDBMS_VERSION 8.1.7.0.0或者查询V$NLS_PARAMETERS表,select * from V$NLS_PARAMETERS;也有类似结果selectto_date(2004-11-12-07-32yy-mm-ddhh24-mi-ss)valuefromdual;VALUE204.11.12 12:07:32select to_date() value from dual;0.15 00:00:00ERROR位于第1行:ORA-01861:文字与格式字符串不匹配sysdate当前日期和时间select sysdate value from dual;3
7、.23 17:09:01last_day本月最后一天select last_day(sysdate) value from dual;30 17:08:17add_months(d,n)日期d后推n个月select add_months(sysdate,2) value from dual;5.10:21next_day(d,day)日期d之后的第一周中,指定的那天(指定星期的第几天)是什么日期SQLselect next_day(sysdate,1) value from dual;28 17:38:55oracle/plsqloracle日期处理完全版日期处理完全版TO_DATE格式Day
8、:dd number 12dy abbreviated friday spelled out fridayddspth spelled out, ordinal twelfthMonth:mm number 03mon abbreviated marmonth spelled out marchYear:yy two digits 98yy four digits 199824小时格式下时间范围为:0:00 - 23:59:59.12小时格式下时间范围为:1:00 - 12:59 .日期和字符转换函数用法(to_date,to_char)2.select to_char( to_date(22
9、2,JJsp) from dual显示Two Hundred Twenty-Two3.求某天是星期几select to_char(to_date(2002-08-26yy-mm-ddday) from dual;星期一selectto_char(to_date(NLS_DATE_LANGUAGE=American) fromdual;monday设置日期语言ALTER SESSION SET NLS_DATE_LANGUAGE=AMERICAN;也可以这样TO_DATE (, YY-mm-ddNLS_DATE_LANGUAGE = American)4.两个日期间的天数select floor
10、(sysdate - to_date(yymmdd) from dual;5.时间为null的用法select id, active_date from table1UNIONselect 1, TO_DATE(null) from dual;注意要用TO_DATE(null)6.a_date between to_date() and to_date()那么12月31号中午12点之后和12月1号的12点之前是不包含在这个范围之内的。所以,当时间需要精确的时候,觉得to_char还是必要的7.日期格式冲突问题输入的格式要看你安装的ORACLE字符集的类型,比如: US7ASCII, date格
11、式的类型就是:01-Jan-01alter system set NLS_DATE_LANGUAGE = Americanalter session set NLS_DATE_LANGUAGE = American或者在to_date中写注意我这只是举了NLS_DATE_LANGUAGE,当然还有很多,可查看select * from nls_session_parametersselect * from V$NLS_PARAMETERS8.select count(*)from ( select rownum-1 rnumfrom all_objectswhere rownum = to_d
12、ate(2002-02-28) - to_date(2002-02-01)+1)where to_char( to_date(2002-02-01)+rnum-1, D )notin ( 17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(01-31-1999MM-DD-YY),to_date(12-31-1998) MONTHS FROM DUAL;1select months_between(to_d
13、ate(02-01-19991.451613 Next_day的用法Next_day(date, day)Monday-Sunday, for format code DAYMon-Sun, for format code DY1-7, for format code D11select 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 isbeginreturn sysdate;e
14、nd;select to_char(sys_date,) from all_objects;12.获得小时数SELECT EXTRACT(HOUR FROM TIMESTAMP 2001-02-16 2:40) from offer select sysdate ,to_char(sysdate,hhSYSDATE TO_CHAR(SYSDATE,HH- -2003-10-13 19:35:21 07hh24HH24- -21 19获取_年_月_日与此类似_年_月_日的处理select older_date,newer_date,years,months,abs(trunc(newer_dat
15、e-add_months( older_date,years*12+months ) daysfrom ( selecttrunc(months_between( newer_date, older_date )/12) YEARS,mod(trunc(months_between( newer_date, older_date ),12 ) MONTHS,older_datefrom ( select hiredate older_date,add_months(hiredate,rownum)+rownum newer_datefrom emp )14.处理月份天数不定的办法selectt
16、o_char(add_months(last_day(sysdate)+1,-2),),last_day(sysdate)from dual16.找出今年的天数select add_months(trunc(sysdate,year), 12) - trunc(sysdate,) from dual闰年的处理方法to_char( last_day( to_date(02 | :year,mmyy) ), dd如果是28就不是闰年yy与rr的区别YY99 TO_C- -yy 99 0099rr 99 1999yy 01 0001rr 01 2001不同时区的处理select to_char( N
17、EW_TIME( sysdate, EST), dd/mm/yy hh:) ,sysdatefrom dual;9.5秒钟一个间隔SelectTO_DATE(FLOOR(TO_CHAR(sysdate,SSS)/300)*300,) ,TO_CHAR(sysdate,from dual2002-11-1 9:55:00 35786SSS表示5位秒数2一年的第几天select TO_CHAR(SYSDATE,DDD),sysdate from dual310 2002-11-6 10:03:51计算小时,分,秒,毫秒selectDays,A,TRUNC(A*24) Hours,TRUNC(A*2
18、4*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) mSecondsfrom(selecttrunc(sysdate) Days,sysdate - trunc(sysdate) Afrom dual)select * from tabnameorder by decode(mode,FIFO,1,-1)*to_char(rq,yymmddhh24miss);/floor(date2-date1) /365)
19、作为年floor(date2-date1, 365) /30)作为月mod(mod(date2-date1, 365), 30)作为日.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。很简单的一句话。把Oracle的日期当作一个特殊数字,以天为单位。可以进行日期+数字=日期,日期-日期=数字,日期-数字=日期MESTAMP数据的格式化显示和DATE数据一样。注意,to_char函数支持date和timestamp,但是trunc却不支持TIMESTAMP数据类型。这已经清楚表明了在当两个时间的差别极度重要的情况下,使用TIMES
20、TAMP数据类型要比DATE数据类型更确切。如果你想显示TIMESTAMP的小数秒信息,参考下面:1SELECT TO_CHAR(time1,MM/DD/YY HH24:SS:FF3) Date FROM date_tableDate-06/20/2003 16:14:00006/26/2003 11:16:36:在上例中,我只现实了小数点后3位的内容。计算timestamp间的数据差别要比老的date数据类型更容易。当你直接相减的话,看看会发生什么。结果将更容易理解,第一行的17天,18小时,27分钟和43秒。1SELECT time1,2time2,3substr(time2-time1)
21、,instr(time2-time1),)+7,2)seconds,4substr(time2-time1),instr(time2-time1),)+4,2)minutes,5substr(time2-time1),instr(time2-time1),)+1,2)hours,6trunc(to_number(substr(time2-time1),1,instr(time2-time1, )days,7trunc(to_number(substr(time2-time1),1,instr(time2-time1,)/7) weeks8*FROM date_tableTIME1TIME2SECONDS MINUTES HOURSDAYS WEEKS- - - - -06/20/2003:00007/08/2003:11:22:57:817206/26/2003:0121这就意味着不再需要关心一天有多少秒在麻烦的计算中。因此,得到天数、月数、天数、时数、分钟数和秒数就成为用substr函数摘取出数字的事情了。系统日期和时间为了得到系统时间,返回成date数据类型。你可以使用sysdate函数。 SELECT SYSDATE FR
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