Oracle MATERIALIZED VIEW -- 物化視圖

1，ORACLE：materialized view和普通VIEW有什麼區別
   materialized view(MV)是自動刷新或者手動刷新的，View不用刷新 MV也可以直接update，但是不影響base table，對View的update反映到base table上 MV主要用於遠程數據訪問，mv中的數據需要佔用磁盤空間，view中不保存數據。

2，權限
   必須具有 RESOURCE 權限和實現化視圖 (Materialized View) 定義中的表的 SELECT 權限。要爲其他用戶創建實現化視圖 (Materialized View)，還必須具有 DBA 權限。

3，創建物化視圖
   CREATE MATERIALIZED VIEW MV_ADDRESS
   nologging
   REFRESH COMPLETE AS 
   SELECT
   trim(ID) as ID
   ,trim(COUNTRY) as COUNTRY
   ,trim(PROV) as PROV
   ,trim(CITY) as CITY
   ,trim(TOWN) as TOWN
   FROM 
   ADDRESS@oracle_dlk;

   COMMENT ON MATERIALIZED VIEW MV_ADDRESS IS '住所表';
   COMMENT ON COLUMN MV_ADDRESS.ID IS 'ID';
   COMMENT ON COLUMN MV_ADDRESS.COUNTRY IS '國家';
   COMMENT ON COLUMN MV_ADDRESS.PROV IS '省份';
   COMMENT ON COLUMN MV_ADDRESS.CITY IS '城市';
   COMMENT ON COLUMN MV_ADDRESS.TOWN IS '城鎮';

4，SQL刷新物化視圖