Oracle时间与字符串的转换
0.日期时间格式Year:yy two digits 两位年 显示值:07yyy three digits 三位年 显示值:007yyyy four digits 四位年 显示值:2007
Month:mm number 两位月 显示值:11mon abbreviated 字符集表示 显示值:11月,若是英文版,显示novmonth spelled out 字符集表示 显示值:11月,若是英文版,显示november
Day:dd number 当月第几天 显示值:02ddd number 当年第几天 显示值:02dy abbreviated 当周第几天简写 显示值:星期五,若是英文版,显示friday spelled out 当周第几天全写 显示值:星期五,若是英文版,显示fridayddspth spelled out, ordinal twelfth
Hour:hh two digits 12小时进制 显示值:01hh24 two digits 24小时进制 显示值:13
Minute:mi two digits 60进制 显示值:45
Second:ss two digits 60进制 显示值:25
其它Q digit 季度 显示值:4WW digit 当年第几周 显示值:44W digit 当月第几周 显示值:1
1. 日期和字符转换函数用法（to_date,to_char）
select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') as nowTime from dual; //日期转化为字符串select to_char(sysdate,'yyyy') as nowYear from dual; //获取时间的年select to_char(sysdate,'mm') as nowMonth from dual; //获取时间的月select to_char(sysdate,'dd') as nowDay from dual; //获取时间的日select to_char(sysdate,'hh24') as nowHour from dual; //获取时间的时select to_char(sysdate,'mi') as nowMinute from dual; //获取时间的分select to_char(sysdate,'ss') as nowSecond from dual; //获取时间的秒
select to_date('2004-05-07 13:23:44','yyyy-mm-dd hh24:mi:ss') from dual//
2. 得到一个数字的拼写--0000-0-0select to_date(2222,'J') from dual;
--TO_CHAR(aDate,'JSP')可以得到一个数字的拼写,TWO MILLION FOUR HUNDRED FIFTY-SIX THOUSAND FOUR HUNDRED
SEVENTY-TWOSELECT TO_CHAR(SYSDATE, 'JSP') FROM DUAL;
--Two Hundred Twenty-Twoselect 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 table1UNIONselect 1, TO_DATE(null) from dual;
注意要用TO_DATE(null)
6.月份差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 = Americanalter 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_parametersselect * from V$NLS_PARAMETERS
8.select count(*)from ( select rownum-1 rnumfrom all_objectswhere 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. 查找月份select months_between(to_date('01-31-1999','MM-DD-YYYY'),to_date('12-31-1998','MM-DD-YYYY')) "MONTHS" FROM
DUAL;1select 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 DAYMon-Sun, for format code DY1-7, for format code D
11select 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;end;
select to_char(sys_date,'hh:mi:ss') from all_objects;
12.获得小时数extract()找出日期或间隔值的字段值SELECT EXTRACT(HOUR FROM TIMESTAMP '2001-02-16 2:38:40') from offerSQL> 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
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 ))) days
from ( selecttrunc(months_between( newer_date, older_date )/12) YEARS,mod(trunc(months_between( newer_date, older_date )),12 ) MONTHS,newer_date,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 0099rrrr 99 1999yyyy 01 0001rrrr 01 2001
18.不同时区的处理select to_char( NEW_TIME( sysdate, 'GMT','EST'), 'dd/mm/yyyy hh:mi:ss') ,sysdatefrom 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 35786SSSSS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selectDays,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)) mSecondsfrom(selecttrunc(sysdate) Days,sysdate - trunc(sysdate) Afrom dual)
select * from tabnameorder by decode(mode,'FIFO',1,-1)*to_char(rq,'yyyymmddhh24miss');
//floor((date2-date1) /365) 作为年floor((date2-date1, 365) /30) 作为月d(mod(date2-date1, 365), 30)作为日.
23.next_day函数 返回下个星期的日期,day为1-7或星期日-星期六,1表示星期日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
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select (sysdate-to_date('2003-12-03 12:55:45','yyyy-mm-dd hh24:mi:ss'))*24*60*60 from ddual日期 返回的是天 然后 转换为ss
24,round[舍入到最接近的日期](day:舍入到最接近的星期日)select sysdate S1,round(sysdate) S2 ,round(sysdate,'year') YEAR,round(sysdate,'month') MONTH ,round(sysdate,'day') DAY from dual
25,trunc[截断到最接近的日期,单位为天] ,返回的是日期类型select sysdate S1,trunc(sysdate) S2, //返回当前日期,无时分秒trunc(sysdate,'year') YEAR, //返回当前年的1月1日,无时分秒trunc(sysdate,'month') MONTH , //返回当前月的1日,无时分秒trunc(sysdate,'day') DAY //返回当前星期的星期天,无时分秒from dual
26,返回日期列表中最晚日期select greatest('01-1月-04','04-1月-04','10-2月-04') from dual
27.计算时间差注:oracle时间差是以天数为单位,所以换算成年月,日
select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))/365) as spanYears from dual
//时间差-年select ceil(moths_between(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))) as spanMonths from dual
//时间差-月select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))) as spanDays from dual //时
间差-天select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))*24) as spanHours from dual
//时间差-时select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))*24*60) as spanMinutes from
dual //时间差-分select floor(to_number(sysdate-to_date('2007-11-02 15:55:03','yyyy-mm-dd hh24:mi:ss'))*24*60*60) as spanSeconds
from dual //时间差-秒
28.更新时间注:oracle时间加减是以天数为单位,设改变量为n,所以换算成年月,日select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),to_char(sysdate+n*365,'yyyy-mm-dd hh24:mi:ss') as newTime from
dual //改变时间-年select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),add_months(sysdate,n) as newTime from dual //改变时间-月select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),to_char(sysdate+n,'yyyy-mm-dd hh24:mi:ss') as newTime from dual //
改变时间-日select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),to_char(sysdate+n/24,'yyyy-mm-dd hh24:mi:ss') as newTime from
dual //改变时间-时select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),to_char(sysdate+n/24/60,'yyyy-mm-dd hh24:mi:ss') as newTime from
dual //改变时间-分select to_char(sysdate,'yyyy-mm-dd hh24:mi:ss'),to_char(sysdate+n/24/60/60,'yyyy-mm-dd hh24:mi:ss') as newTime
from dual //改变时间-秒
29.查找月的第一天,最后一天SELECT Trunc(Trunc(SYSDATE, 'MONTH') - 1, 'MONTH') First_Day_Last_Month,Trunc(SYSDATE, 'MONTH') - 1 / 86400 Last_Day_Last_Month,Trunc(SYSDATE, 'MONTH') First_Day_Cur_Month,LAST_DAY(Trunc(SYSDATE, 'MONTH')) + 1 - 1 / 86400 Last_Day_Cur_MonthFROM dual;
30.TO_CHAR 是把日期或数字转换为字符串TO_DATE 是把字符串转换为数据库中得日期类型转换函数TO_NUMBER 将字符转化为数字
TO_CHAR使用TO_CHAR函数处理数字TO_CHAR(number, '格式')TO_CHAR(salary,’$99,999.99’);使用TO_CHAR函数处理日期TO_CHAR(date,’格式’);
TO_NUMBER使用TO_NUMBER函数将字符转换为数字TO_NUMBER(char[, '格式'])
TO_DATE使用TO_DATE函数将字符转换为日期TO_DATE(char[, '格式'])
数字格式格式9 代表一个数字0 强制显示0$ 放置一个$符L 放置一个浮动本地货币符. 显示小数点, 显示千位指示符