闪回查询

chenghuaming

select salary from employees as of timestamp to_timestamp('2016-11-22:21:52:02','YYYY-MM-DD:HH24:MI:SS')
  2     where  employee_id=100;

    SALARY
----------
     30000

SQL>  select salary from employees  where  employee_id=100;

    SALARY
----------
     30001

select salary from employees as of timestamp to_timestamp('2016-11-22:21:52:02','YYYY-MM-DD:HH24:MI:SS')
  2     where  employee_id=100;

    SALARY
----------
     30000

select salary from employees as of timestamp to_timestamp('2016-11-22:21:52:02','YYYY-MM-DD:HH24:MI:SS')
  2     where  employee_id=100;

    SALARY
----------
     30000

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SQL> conn sys/oracle_4U as sysdba;
Connected.
SQL> alter system flush buffer_cache;

System altered.

SQL> alter system flush buffer_cache;

System altered.

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唐老师，内存刷了很多次，为什么旧值还是可以查到

botang

要把旧的undo表空间删除后，刷内存。