select to_char(sysdate,'yyyy-MM-dd HH24:mi:ss') from dual;
select to_date('2005-01-01 13:14:20','yyyy-MM-dd HH24:mi:ss') from dual;
to_date() function
1.日期格式参数 含义说明
D 一周中的星期几
DAY 天的名字，使用空格填充到9个字符
DD 月中的第几天
DDD 年中的第几天
DY 天的简写名
IW ISO标准的年中的第几周
IYYY ISO标准的四位年份
YYYY 四位年份
YYY,YY,Y 年份的最后三位，两位，一位
HH 小时，按12小时计
HH24 小时，按24小时计
MI 分
SS 秒
MM 月
Mon 月份的简写
Month 月份的全名
W 该月的第几个星期
WW 年中的第几个星期 1.日期时间间隔操作
当前时间减去7分钟的时间
select sysdate,sysdate - interval '7' MINUTE from dual
当前时间减去7小时的时间
select sysdate - interval '7' hour from dual
当前时间减去7天的时间
select sysdate - interval '7' day from dual
当前时间减去7月的时间
select sysdate,sysdate - interval '7' month from dual
当前时间减去7年的时间
select sysdate,sysdate - interval '7' year from dual
时间间隔乘以一个数字
select sysdate,sysdate - 8 *interval '2' hour from dual
2.日期到字符操作
select sysdate,to_char(sysdate,'yyyy-mm-dd hh24:mi:ss') from dual
select sysdate,to_char(sysdate,'yyyy-mm-dd hh:mi:ss') from dual
select sysdate,to_char(sysdate,'yyyy-ddd hh:mi:ss') from dual
select sysdate,to_char(sysdate,'yyyy-mm iw-d hh:mi:ss') from dual
参考oracle的相关关文档(ORACLE901DOC/SERVER.901/A90125/SQL_ELEMENTS4.HTM#48515)
3. 字符到日期操作
select to_date('2003-10-17 21:15:37','yyyy-mm-dd hh24:mi:ss') from dual
具体用法和上面的to_char差不多。
4. trunk/ ROUND函数的使用
select trunc(sysdate ,'YEAR') from dual
select trunc(sysdate ) from dual
select to_char(trunc(sysdate ,'YYYY'),'YYYY') from dual
5.oracle有毫秒级的数据类型
--返回当前时间 年月日小时分秒毫秒
select to_char(current_timestamp(5),'DD-MON-YYYY HH24:MI:SSxFF') from dual;
--返回当前 时间的秒毫秒，可以指定秒后面的精度(最大=9)
select to_char(current_timestamp(9),'MI:SSxFF') from dual;
6.计算程序运行的时间(ms)
declare
type rc is ref cursor;
l_rc rc;
l_dummy all_objects.object_name%type;
l_start number default dbms_utility.get_time;
begin
for I in 1 .. 1000
loop
open l_rc for
'select object_name from all_objects '||
'where object_id = ' || i;
fetch l_rc into l_dummy;
close l_rc;
end loop;
dbms_output.put_line
( round( (dbms_utility.get_time-l_start)/100, 2 ) ||
' seconds...' );
end;
to_char() function
The following are number examples for the to_char function.
|
to_char(1210.73, '9999.9') |
would return '1210.7' |
|
to_char(1210.73, '9,999.99') |
would return '1,210.73' |
|
to_char(1210.73, '$9,999.00') |
would return '$1,210.73' |
|
to_char(21, '000099') |
would return '000021' |
|
Parameter |
Explanation |
|
YEAR |
Year, spelled out |
|
YYYY |
4-digit year |
|
YYY |
Last 3, 2, or 1 digit(s) of year. |
|
IYY |
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. |
The following are date examples for the to_char function.
|
to_char(sysdate, 'yyyy/mm/dd'); |
would return '2003/07/09' |
|
to_char(sysdate, 'Month DD, YYYY'); |
would return 'July 09, 2003' |
|
to_char(sysdate, 'FMMonth DD, YYYY'); |
would return 'July 9, 2003' |
|
to_char(sysdate, 'MON DDth, YYYY'); |
would return 'JUL 09TH, 2003' |
|
to_char(sysdate, 'FMMON DDth, YYYY'); |
would return 'JUL 9TH, 2003' |
|
to_char(sysdate, 'FMMon ddth, YYYY'); |
would return 'Jul 9th, 2003' |
You will notice that in some examples, the format_mask parameter begins with "FM". This means that zeros and blanks are suppressed. This can be seen in the examples below.
|
to_char(sysdate, 'FMMonth DD, YYYY'); |
would return 'July 9, 2003' |
|
to_char(sysdate, 'FMMON DDth, YYYY'); |
would return 'JUL 9TH, 2003' |
|
to_char(sysdate, 'FMMon ddth, YYYY'); |
would return 'Jul 9th, 2003' |
The zeros have been suppressed so that the day component shows as "9" as opposed to "09".