建物化視圖，完成query rewrite,refresh功能

1、創建物化視圖

TEST8@ odb>create materialized view  v_wuhua as select * from gaoshuiwei;

create materialized view v_001 asselect * from gaoshuiwei

                                               *

ERROR at line 1:

ORA-01031: insufficient privileges

sys@ odb>grant create materialized view to test8;

TEST8@ odb>create materializedview v_wuhua as select * from gaoshuiwei;

 Materialized view created.

TEST8@ odb>create view v_shituas select * from gaoshuiwei;

create view v_shitu as select *from gaoshuiwei

            *

ERROR at line 1:

ORA-01031: insufficient privileges

sys@ odb>grant create view to test8;

TEST8@ odb>create view v_shituas select * from gaoshuiwei;

 View created.

清空v_wuhua數據提示數據操作不合法，說明物化視圖只能讀不能刪除數據，

1、比較物化視圖和視圖的區別

TEST8@odb>delete from gaoshuiwei;    //清空基表

68310rows deleted.

查詢物化視圖和普通視圖的區別

TEST8@odb>select count(*) from v_wuhua;

  COUNT(*)

----------

     68310

TEST8@odb>select count(*) from v_shitu;

  COUNT(*)

----------

         0

可以看到隨著基表的被清空，物化視圖是沒有變化的，而普通視圖隨之清空；重新插入數據效果還是一樣物化視圖不變，普通視圖隨著基表的變化而變化

TEST8@odb>insert into gaoshuiwei select * from all_objects;

68314rows created.

TEST8@odb>commit;

Commitcomplete.

TEST8@odb>select count(*) from gaoshuiwei;

  COUNT(*)

----------

     68314

TEST8@odb>select count(*) from v_wuhua;

  COUNT(*)

----------

     68310

TEST8@odb>select count(*) from v_shitu;

  COUNT(*)

----------

     68314

TEST8@odb>exec dbms_mview.refresh('V_WUHUA');  //刷新物化視圖數據這時和基表數據一致了。

物化視圖不僅可以全量的刷新數據還可以增量的刷新數據；

TEST8@odb>create materialized view v_wuhua1 as select * from gaoshuiwei whererownum<1;

Materializedview created.

TEST8@odb>select count(*) from v_wuhua1;

  COUNT(*)

----------

         0

selectdbms_metadata.get_ddl('MATERIALIZED_VIEW','V_WUHUA1','TEST8') FROM DUAL;

3、查詢重寫

TEST8@odb>create materialized view v_wuhua3 enable query rewrite as select * fromgaoshuiwei;

 Materializedview created.

看一下基表的查詢執行計劃，執行計劃上看表面查詢的是基表實際上查詢的是物化視圖；

4、刪除物化視圖

DROPMATERIALIZED VIEW V_TESTMV;