Oracle to_char的时间数据格式转换

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：

Parameter	Explanation
YEAR	Year, spelled out
YYYY	4-digit year
YYY YY Y	Last 3, 2, or 1 digit(s) of year.
IYY IY I	Last 3, 2, or 1 digit(s) of ISO year.
IYYY	4-digit year based on the ISO standard
Q	Quarter of year (1, 2, 3, 4; JAN-MAR = 1).
MM	Month (01-12; JAN = 01).
MON	Abbreviated name of month.
MONTH	Name of month, padded with blanks to length of 9 characters.
RM	Roman numeral month (I-XII; JAN = I).
WW	Week of year (1-53) where week 1 starts on the first day of the year and continues to the seventh day of the year.
W	Week of month (1-5) where week 1 starts on the first day of the month and ends on the seventh.
IW	Week of year (1-52 or 1-53) based on the ISO standard.
D	Day of week (1-7).
DAY	Name of day.
DD	Day of month (1-31).
DDD	Day of year (1-366).
DY	Abbreviated name of day.
J	Julian day; the number of days since January 1, 4712 BC.
HH	Hour of day (1-12).
HH12	Hour of day (1-12).
HH24	Hour of day (0-23).
MI	Minute (0-59).
SS	Second (0-59).
SSSSS	Seconds past midnight (0-86399).
FF	Fractional seconds.

其他语言objective-c的date格式转换，参考

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