oracle hint

sample 1:

select /*+INDEX(t IDX_SEL_ADD_DATE)*/ t.own_sys, count(1)
 from std_entp_login t
where t.add_date >
              to_date('2010-12-28 00:00:00', 'yyyy-mm-dd hh24:mi:ss')
          and t.add_date <
              to_date('2010-12-28 23:59:59', 'yyyy-mm-dd hh24:mi:ss')
group by t.own_sys

用到别名时，/*+INDEX(TABLE INDEX_NAME)*/中的TABLE一定是别名，否则不走执行强制索引。

ref

http://www.cnblogs.com/ebs-blog/archive/2011/09/05/2167730.html