Oracle to_char的时间数据格式转换

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Oracle to_char的一些功能记录。

1、转成年月日时分秒的操作；

2、转成微妙的操作

SQL> select to_char(systimestamp, 'yyyy-mm-dd-hh24:mi:ss.ff') from dual;

TO_CHAR(SYSTIMESTAMP,'YYYY-MM-
------------------------------
2013-09-26-16:08:04.234000

注意，没有转成毫秒的参数格式。

如果需要转成毫秒，这样操作

SQL> select to_char(systimestamp, 'yyyy-mm-dd-hh24:mi:ss.ff3') from dual;

TO_CHAR(SYSTIMESTAMP,'YYYY-MM-
------------------------------
2013-09-26-16:12:10.640

3、转成零点到当前时间的秒数

SQL> select to_char(systimestamp, 'yyyymmddhh24miss -- SSSSS') from dual;

TO_CHAR(SYSTIMESTAMP,'YYYYMMDD
------------------------------
20130926160938 -- 58178

SQL> select to_char(systimestamp, 'yyyy-mm-dd-hh24:mi:ss'),

2         to_char(systimestamp, 'yyyymmddhh24miss -- SSSSS'),
3         to_char(systimestamp, 'hh24') * 60 * 60 +
4         to_char(systimestamp, 'mi') * 60 + to_char(systimestamp, 'ss') +
5         to_number(to_char(systimestamp, 'ff') / 1000000.00)
6    from dual
7 /

TO_CHAR(SYSTIMESTAMP,'YYYY-MM- TO_CHAR(SYSTIMESTAMP,'YYYYMMDD TO_CHAR(SYSTIMESTAMP,'HH24')*6
------------------------------ ------------------------------ ------------------------------
2013-09-26-16:00:13            20130926160013 -- 57613                                 57613

其他参数如下表所示：

ParameterExplanationYEARYear, spelled outYYYY4-digit yearYYY
YY
YLast 3, 2, or 1 digit(s) of year.IYY
IY
ILast 3, 2, or 1 digit(s) of ISO year.IYYY4-digit year based on the ISO standardQQuarter of year (1, 2, 3, 4; JAN-MAR = 1).MMMonth (01-12; JAN = 01).MONAbbreviated name of month.MONTHName of month, padded with blanks to length of 9 characters.RMRoman numeral month (I-XII; JAN = I).WWWeek of year (1-53) where week 1 starts on the first day of the year and continues to the seventh day of the year.WWeek of month (1-5) where week 1 starts on the first day of the month and ends on the seventh.IWWeek of year (1-52 or 1-53) based on the ISO standard.DDay of week (1-7).DAYName of day.DDDay of month (1-31).DDDDay of year (1-366).DYAbbreviated name of day.JJulian day; the number of days since January 1, 4712 BC.HHHour of day (1-12).HH12Hour of day (1-12).HH24Hour of day (0-23).MIMinute (0-59).SSSecond (0-59).SSSSSSeconds past midnight (0-86399).FFFractional seconds.

其他语言objective-c的date格式转换，参考

http://userguide.icu-project.org/formatparse/datetime