建物化视图，完成query rewrite,refresh功能

1、创建物化视图

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数据提示数据操作不合法，说明物化视图只能读不能删除数据，

1、比较物化视图和视图的区别

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

68310rows deleted.

查询物化视图和普通视图的区别

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

COUNT(*)

----------

68310

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

COUNT(*)

----------

0

可以看到随着基表的被清空，物化视图是没有变化的，而普通视图随之清空；重新插入数据效果还是一样物化视图不变，普通视图随着基表的变化而变化

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'); //刷新物化视图数据这时和基表数据一致了。

物化视图不仅可以全量的刷新数据还可以增量的刷新数据；

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、查询重写

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

Materializedview created.

看一下基表的查询执行计划，执行计划上看表面查询的是基表实际上查询的是物化视图；

4、删除物化视图

DROPMATERIALIZED VIEW V_TESTMV;

（编辑：李大同）

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