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Which three options are true about MVIEWs?
A. The defining query of an MVIEWs may be based on a populated table.
B. Queries that are rewritten to an MVIEW will never obtain results from the result cache.
C. All MVIEWS may be configured to support “refresh on demand”.
D. The defining query of an MVIEW may be based on non_partitioned table.
E. All MVIEWs may be configured to support “refresh on commit”
Correct Answer: ABC
Explanation/Reference:
A:The defining query of a materialized view can select from tables, views, or materialized views owned by the user SYS, but you cannot enable QUERY REWRITE on such a materialized view.
B:You cannot specify the following CREATE MATERIALIZED VIEW clauses: CACHE or NOCACHE, CLUSTER, or ON PREBUILT TABLE.
C:Specify ON DEMAND to indicate that the materialized view will be refreshed on demand by calling one of the three DBMS_MVIEW refresh procedures. If you omit both ON COMMIT and ON DEMAND, ON DEMAND is the default.
Incorrect:
E:Materialized views can only refresh ON COMMIT in certain situations.
The materialized view cannot contain object types or Oracle-supplied types.
The base tables will never have any distributed transactions applied to them.
Note:
*Oracle uses materialized views (also known as snapshots in prior releases) to replicate data to non-master sites in a replication environment and to cache expensive queries in a data warehouse environment.
*A materialized view is a replica of a target master from a single point in time. The master can be either a master table at a master site or a master materialized view at a materialized view site. Whereas in multimaster replication tables are continuously updated by other master sites, materialized views are updated from one or more masters through individual batch updates, known as a refreshes, from a single master site or master materialized view site.
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