oracle 时间函数to_date

TO_DATE Format Masks
Format	Returns
D	Day of the week
DD	Day of the month
DDD	Numerical day of the year, 1 ~ 365 (366 for Leap years)
DAY	Full textual representation of the day, i.e. "Monday", "Tuesday", "Wednesday"
DY	Day in three letters, i.e. "MON", "TUE", "FRI"
W	Week of the month
WW	Week of the year
MM	Month in two digits, i.e. 01 = Jan, 02 = Feb,...12 = -Dec
MON	Month in three characters, i.e. "Jan", "Feb", "Apr"
MONTH	Full textual representation of the Month, i.e. "January", "February", "April"
RM	Month in Roman Characters (I-XII, I-Jan, II-Feb, ... XII-Dec)
Q	Quarter of the Month
YY	Last two digits of the year.
YYYY	Full year
YEAR	Year in words like "Nineteen Eighty Seven"
HH	Hours in 12 hour format
HH12	Hours in 12 hour format
HH24	Hours in 24 hour format ("military time")
MI	Minutes
SS	Seconds
FF	Fractional Seconds
SSSSS	Milliseconds
J	Julian Day i.e Days since 1st-Jan-4712BC to till-date
RR	If the year is less than 50 then Oracle considers the year as a 21st century date. If the year is greater than 50 then Oracle considers the year to be in the 20th century.

字符串转变成date

SQL> SELECT TO_DATE('2014-4-10 14:10:00', 'YYYY-MM-DD HH24:MI:SS') FROM DUAL;
 
TO_DATE('2014-4-1014:10:00','Y
------------------------------
2014-4-10 14:10:00

获得当前时间

SQL> SELECT SYSDATE FROM DUAL;
 
SYSDATE
------------------------------
2014-4-10 10:28:33

格式化时间

SQL> SELECT TO_CHAR(SYSDATE, 'YYYY-MM-DD HH24:MI:SS') FROM DUAL;
 
TO_CHAR(SYSDATE,'YYYY-MM-DDHH2
------------------------------
2014-04-10 10:22:43
 
SQL>

12小时制

SQL> SELECT TO_CHAR(SYSDATE, 'YYYY-MM-DD HH24:MI:SS') FROM DUAL;
 
TO_CHAR(SYSDATE,'YYYY-MM-DDHH2
------------------------------
2014-04-10 13:24:03
 
SQL> SELECT TO_CHAR(SYSDATE, 'YYYY-MM-DD HH:MI:SS') FROM DUAL;
 
TO_CHAR(SYSDATE,'YYYY-MM-DDHH:
------------------------------
2014-04-10 01:24:06
 
SQL>