What privilege is required for materialized view?
To create a materialized view in another user’s schema: You must have the CREATE ANY MATERIALIZED VIEW system privilege. The owner of the materialized view must have the CREATE TABLE system privilege.
What is the difference between materialized view and view materialized view?
Views are generally used when data is to be accessed infrequently and data in table get updated on frequent basis. On other hand Materialized Views are used when data is to be accessed frequently and data in table not get updated on frequent basis.
Why does materialized view become invalid?
When an MV is created, the materialized view depends on the master tables referenced in its definition. Any DML operation, such as an INSERT, or DELETE, UPDATE, or DDL operation on any dependency in the materialized view will cause it to become invalid.
What is a limitation of materialized view?
Materialized views use a restricted SQL syntax and a limited set of aggregation functions. For more information, see Supported materialized views. Materialized views cannot be nested on other materialized views. Materialized views cannot query external tables.
Can you create or replace materialized view?
No, you cannot alter the query of a materialized view without dropping it. The CREATE MATERIALIZED VIEW syntax does not support that feature. The ALTER MATERIALIZED VIEW is used to modify an existing materialized view in one or more of the following ways: To change its storage characteristics.
How can materialized view refresh automatically in Oracle?
Set the initialization parameters and bounce the database. Create the materialized view table. Here, we specify that the materialized view will be refreshed every two hours with the refresh fast option. Instead of using DBMS_MVIEW, you can automatically refresh the MVIEW (Snapshot) using Oracle DBMS_JOB Management.
Why we use materialized view instead of a table?
So here comes Materialized views helps us to get data faster. Materialized views are physically exist in database. Whenever the base table is updated the Materialized view gets updated. Materialized views are updated periodically based upon the query definition, table can not do this.
Can we perform DML on materialized view?
A materialized view can be either read-only, updatable, or writeable. Users cannot perform data manipulation language (DML) statements on read-only materialized views, but they can perform DML on updatable and writeable materialized views.
How do I make a materialized view valid?
The materialized view must be in your own schema, or you must have the ALTER ANY MATERIALIZED VIEW system privilege. To enable a materialized view for query rewrite: If all of the master tables in the materialized view are in your schema, you must have the QUERY REWRITE privilege.
How do you refresh materialized view?
To update the data in a materialized view, you can use the REFRESH MATERIALIZED VIEW statement at any time. When you use this statement, Amazon Redshift identifies changes that have taken place in the base table or tables, and then applies those changes to the materialized view.
Why use materialized view instead of a table?
A materialized view is a pre-computed data set derived from a query specification (the SELECT in the view definition) and stored for later use. Because the data is pre-computed, querying a materialized view is faster than executing a query against the base table of the view.
Why materialized view is faster than view?
On comparison, the materialized view responds faster than light because the materialized view is pre-computed and stored on disk. So, it does not require any extra time in resolving queries each time. This results in the Materialized View responses faster than standard View.
Can materialized view have index?
A materialized view can be partitioned, and you can define a materialized view on a partitioned table. You can also define one or more indexes on the materialized view.
What is fast refresh in materialized view?
A fast refresh requires having a materialized view log on the source tables that keeps track of all changes since the last refresh, so any new refresh only has changed (updated, new, deleted) data applied to the MV. A complete refresh does what it says: it completely refreshes all data in the MV.
Can we delete data from materialized view?
You cannot delete rows from a read-only materialized view. If you delete rows from a writable materialized view, then the database removes the rows from the underlying container table. However, the deletions are overwritten at the next refresh operation.
Can we use joins in materialized view?
One of the most common follow-on questions we receive is whether materialized views can support joins. The answer is emphatically yes.
Why do we need materialized views?
You can use materialized views to achieve one or more of the following goals: Ease Network Loads. Create a Mass Deployment Environment. Enable Data Subsetting.
Can we use DML in materialized view?
Why materialized view is faster?
Materialized views are faster than tables because of their “cache” (i.e. the query results for the view); in addition, if data has changed, they can use their “cache” for data that hasn’t changed and use the base table for any data that has changed.
Can materialized view have primary key?
WITH PRIMARY KEY Clause
Primary key materialized views allow materialized view master tables to be reorganized without affecting the eligibility of the materialized view for fast refresh. The master table must contain an enabled primary key constraint.
Does materialized view store data?
What happens to materialized view if table is dropped?
If you drop a materialized view, then any compiled requests that were rewritten to use the materialized view will be invalidated and recompiled automatically. If the materialized view was prebuilt on a table, then the table is not dropped, but it can no longer be maintained by the materialized view refresh mechanism.
Can we create materialized view on multiple tables?
– You cannot create a fast refreshable materialized view from multiple tables with simple joins that include an object type column in the SELECT statement.
Can we create index on materialized view Oracle?
A materialized view can be partitioned, and you can define a materialized view on a partitioned table. You can also define one or more indexes on the materialized view. Unlike indexes, materialized views can be accessed directly using a SELECT statement.