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
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其他参数如下表所示：
parameterexplanation
yearyear, spelled out
yyyy4-digit year
yyy
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 standard
qquarter 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
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