What is the difference between materialized view and view materialized view?
Differences between Views and Materialized Views:
| Views | Materialized Views |
|---|---|
| Query expression are stored in the databases system, and not the resulting tuples of the query expression. | Resulting tuples of the query expression are stored in the databases system. |
Can we create materialized view on view in Oracle?
When you create a materialized view, Oracle Database creates one internal table and at least one index, and may create one view, all in the schema of the materialized view. Oracle Database uses these objects to maintain the materialized view data. You must have the privileges necessary to create these objects.
Are materialized views faster than views?
Materialized View responds faster in comparison to View. It is because the materialized view is precomputed and hence, it does not waste time in resolving the query or joins in the query that creates the Materialized View. Which in turn responses faster to the query made on materialized view.
Can we do 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.
What is the purpose of materialized view?
In data warehouses, you can use materialized views to precompute and store aggregated data such as the sum of sales. Materialized views in these environments are often referred to as summaries, because they store summarized data. They can also be used to precompute joins with or without aggregations.
What is the advantage of materialized view?
Benefits of using materialized views Reduce the execution time for complex queries with JOINs and aggregate functions. The more complex the query, the higher the potential for execution-time saving. The most benefit is gained when a query’s computation cost is high and the resulting data set is small.
Can we create primary key on materialized view?
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. You cannot specify this clause for an object materialized view.
What are the benefits of materialized view?
A properly designed materialized view provides the following benefits:
- Reduce the execution time for complex queries with JOINs and aggregate functions.
- The optimizer in dedicated SQL pool can automatically use deployed materialized views to improve query execution plans.
- Require low maintenance on the views.
Can materialized views be partitioned?
You can partition materialized views like you can partition tables. When the database rewrites a query to run against materialized views, the query can take advantage of the same performance features from which queries running against tables directly benefit.
What is a materialized view in Oracle?
Materialized Views in Oracle. A materialized view, or snapshot as they were previously known, is a table segment whose contents are periodically refreshed based on a query, either against a local or remote table.
How are the base tables connected in a materialized view?
The base tables referenced in the materialized view’s defining query must be connected in a join graph that uses the star schema or snowflake schema model. The query must contain exactly one centralized fact table and one or more dimension tables, with all pairs of joined tables being related using primary key-foreign key constraints.
What are the requirements for an updatable materialized view?
An updatable materialized view must belong to a materialized view group that has the same name as the replication group at its master site or master materialized view site. In addition, an updatable materialized view must reside in a different database than the master replication group.
Why does Oracle database return an error when I REFRESH MATERIALIZED views?
If the materialized view is not eligible for fast refresh, then Oracle Database returns an error when you attempt to refresh this view. Materialized views are not eligible for fast refresh if the defining query contains an analytic function or the XMLTable function.