oracle日期函数2！

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;

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