What is Oracle materialized view log?

In an Oracle database, a materialized view log is a table associated with the master table of a materialized view. Rows are automatically added to the Materialized View Log table when the master table changes. The Oracle database uses the materialized view log to refresh materialized views based on the master table.

How do I create a materialized view log in Oracle?

Oracle Database creates the materialized view log in the schema of its master table. You cannot create a materialized view log for a table in the schema of the user SYS . Specify the name of the master table for which the materialized view log is to be created.

How do I view materialized view logs?

all_mview_logs will show you all the materialized view logs that you have access to. user_mview_logs will show you all the materialized view logs that you own.

What’s the purpose of a materialized view log when is it required?

Materialized View Logs in Oracle A materialized view log is required on a master if we want to fast refresh materialized views based on the master. When we create a materialized view log for a master table or master materialized view, Oracle creates an underlying table as the materialized view log.

What is the difference between view and materialized view?

The basic difference between View and Materialized View is that Views are not stored physically on the disk. View can be defined as a virtual table created as a result of the query expression. However, Materialized View is a physical copy, picture or snapshot of the base table.

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.

What is difference between view and materialized view?

What is the difference between materialized view and table?

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. A materialized view can be set up to refresh automatically on a periodic basis. A table may need additional code to truncate/reload data.

How do you create a materialized view?

Use the CREATE MATERIALIZED VIEW statement to create a materialized view. A materialized view is a database object that contains the results of a query. The FROM clause of the query can name tables, views, and other materialized views.

What is the purpose of materialized view?

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.

What is meant by materialized view?

A materialized view is a database object that contains the results of a query. You can select data from a materialized view as you would from a table or view. In replication environments, the materialized views commonly created are primary key, rowid, object, and subquery materialized views.

Why do we need materialized view?

The Need for Materialized Views You can use materialized views to increase the speed of queries on very large databases. Queries to large databases often involve joins between tables, aggregations such as SUM , or both. These operations are expensive in terms of time and processing power.

Why do we use materialized view in Oracle?

Materialized View Concepts 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.

When to use a materialized view?

Materialized views are primarily used to increase application performance when it isn’t feasible or desirable to use a standard view with indexes applied to it. Materialized views can be updated on a regular basis either through triggers or by using the ON COMMIT REFRESH option.

Is materialized view refreshed automatically?

A materialized view can be refreshed automatically using the ON COMMIT method. Therefore, whenever a transaction commits which has updated the tables on which a materialized view is defined, those changes are automatically reflected in the materialized view.

Can I rename a materialized view?

Such materialized views can be queried but can’t be refreshed. In this case, you must drop and recreate the materialized view. In general, you can’t alter a materialized view’s definition (its SQL statement). You can’t rename a materialized view.