oracle dba的练习 恢复数据 with as去重

http://blog.sina.com.cn/s/articlelist_2120624970_0_1.html

http://blog.csdn.net/fw0124/article/details/6210730

恢复数据
select * from table as of timestamp to_date('2011-01-19 15:28:00', 'yyyy-mm-dd hh24:mi:ss')

    SQL> with employee_avg_salary as (  
      2  select employee_id, avg(salary) avg_salary from salary  
      3  group by employee_id)  
      4  select * from employee_avg_salary t  
      5  where t.avg_salary>(select avg(avg_salary)
    from employee_avg_salary)  
      6  /  
     
    EMPLOYEE_ID   AVG_SALARY  
    -----------  ------------  
         1             8500  
         2             6800