( 2）通過唯一rowid實現刪除重複記錄.在Oracle中，每一條記錄都有一個rowid，rowid在整個資料庫中是唯一的，rowid確定了每條記 錄是在Oracle中的哪一個資料檔案、塊、行上。在重複的記錄中，可能所有列的內容都相同，但rowid不會相同，所以只要確定出重複記錄中那些具有最 大或最小rowid的就可以了，其餘全部刪除。

　　SQL>delete from employee e2 where rowid not in (
　　select max(e1.rowid) from employee e1 where

　　e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and e1.salary=e2.salary);--這裡用min(rowid)也可以。

　　SQL>delete from employee e2 where rowid <(
　　select max(e1.rowid) from employee e1 where
　　e1.emp_id=e2.emp_id and e1.emp_name=e2.emp_name and e1.salary=e2.salary);

　　（3）也是通過rowid，但效率更高。

另：

create table t_asset_attribute_temp as (select distinct account_id,asset_id,attributes_constraint, attributes_display_name,

     attributes_id, attributes_name, attributes_type, required, "value",created_by from t_asset_attribute 

     where (attributes_name='outsidePhoto' or attributes_name='insidePhoto')  and account_id in (select account_id from t_account_business where business_type=2));

delete from t_asset_attribute where (attributes_name='outsidePhoto' or attributes_name='insidePhoto') and account_id in (select account_id from t_account_business where business_type=2);

insert into t_asset_attribute (account_id,asset_id,attributes_constraint, attributes_display_name,

     attributes_id, attributes_name, attributes_type, required, "value",created_by) select ta.account_id,ta.asset_id,ta.attributes_constraint, ta.attributes_display_name, 

     ta.attributes_id, ta.attributes_name, ta.attributes_type, ta.required, ta."value",ta.created_by from t_asset_attribute_temp ta;

drop table t_asset_attribute_temp;