这篇文章主要介绍了oracle中to_date详细用法示例,包括期和字符转换函数用法、字符串和时间互转、求某天是星期几、两个日期间的天数、月份差等用法
TO_DATE格式(以时间:2007-11-02 13:45:25为例)
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
2. 字符串和时间互转
select to_date('2004-05-07 13:23:44','yyyy-mm-dd hh24:mi:ss') from dualselect 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 table1 UNION select 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 = 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 8.查询特殊条件天数
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. 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; //结果为：1 select months_between(to_date('02-01-1999','MM-DD-YYYY'),to_date('12-31-1998','MM-DD-YYYY')) "MONTHS" FROM DUAL; //结果为：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.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 offer select sysdate ,to_char(sysdate,'hh') from dual; SYSDATE TO_CHAR(SYSDATE,'HH') -------------------- --------------------- 2003-10-13 19:35:21 07 select sysdate ,to_char(sysdate,'hh24') from dual; SYSDATE TO_CHAR(SYSDATE,'HH24') -------------------- ----------------------- 2003-10-13 19:35:21 19
12.年月日的处理
SELECT older_date, newer_date, years, months, ABS ( TRUNC ( newer_date - ADD_MONTHS (older_date, years * 12 + months) ) ) daysFROM ( 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 ) )
13.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
14.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 15.yyyy与rrrr的区别
YYYY99 TO_C ------- ---- yyyy 99 0099 rrrr 99 1999 yyyy 01 0001 rrrr 01 2001
16.不同时区的处理
select to_char( NEW_TIME( sysdate, 'GMT','EST'), 'dd/mm/yyyy hh:mi:ss') ,sysdate from dual;
17. 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
18.一年的第几天
select TO_CHAR(SYSDATE,'DDD'),sysdate from dual //310 2002-11-6 10:03:51
19.计算小时,分,秒,毫秒
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 ) SELECT * FROM tabname ORDER 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.
20.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 select (sysdate-to_date('2003-12-03 12:55:45','yyyy-mm-dd hh24:mi:ss'))*24*60*60 from dual//日期 返回的是天 然后 转换为ss 21,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
22,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
23,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 24.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 25.更新时间
//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
26.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;