oracle日期函数2！

1.日期时间间隔操作

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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

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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)

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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。

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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

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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;

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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;

http://www.cnblogs.com/fjfzhkb/archive/2007/10/26/938421.html