Ubuntu 9.04安装Oracle 11，备案!!

代码:

The first time that a read is performed on a table results in that view of the table being preserved throughout that transaction.
在一个事务中，当第一次读一张表时，会立即被保存该表的一个视图。

Any changes made on that table committed by other transactions after that point are not seen.
在这之后，任何其他事务对这个表的改变本事务是看不到的。

However, if a different transaction commits a change between the time that you start your transaction and the time that you perform your first read on that table, you will see the changes made by that other transaction.
但是，如果一个不同的事务在你开启事务后第一次读之前提交了对该表的一个更新，你可以看到这些事务提交的改变。

代码:

              trsaction1             trsaction2
time1         read  i
time2                                        read i
time3         ++i并提交事务               
time4                                   ++i提交事务