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Validating Tables, Indexes, Clusters, and Materialized Views → To verify the integrity of the structure of a table, index, cluster, or materialized view, use the … cluster is corrupt, you should drop it and re-create it. If a materialized view is corrupt, perform … , drop and re-create the materialized view. The following statement analyzes the emp table: ANALYZE
Materialized Views → … The new names appear in all data dictionary views, but both the old and new names are accepted by the … GRANT and REVOKE SQL statements. CREATE SNAPSHOT changed to CREATE MATERIALIZED VIEW CREATE ANY … SNAPSHOT changed to CREATE ANY MATERIALIZED VIEW ALTER ANY SNAPSHOT changed to ALTER ANY MATERIALIZED
Naming Materialized Views → , you might consider extending this naming scheme to the materialized views so that they are easily … The name of a materialized view must conform to standard Oracle naming conventions. However, if the … materialized view is based on a user-defined prebuilt table, then the name of the materialized view
Materialized Views and Models → Examples of Materialized Views Using UNION ALL The following examples illustrate creation of fast … refreshable materialized views involving UNION ALL. Example 10-5 Materialized View Using UNION ALL … with Two Join Views To create a UNION ALL materialized view with two
Invalidating Materialized Views → Dependencies related to materialized views are automatically maintained to ensure correct operation … views is not tracked. Thus, if you use remote materialized views for rewrite, they are considered to be trusted. … . When a materialized view is created, the materialized
Creating Materialized Views → Why Use Nested Materialized Views? In a data warehouse, you typically create many aggregate views … distinct materialized aggregate views can take a long time, because the underlying join has to be … performed many times. Using nested materialized views, you can create
Compressing Materialized Views → foreign keys. In particular, materialized views created with the ROLLUP clause are likely candidates
Characteristics of Materialized Views → views Oracle Database SQL Language Reference to learn about the CREATE MATERIALIZED VIEW statement … Characteristics of Materialized Views Materialized views share some characteristics of nonmaterialized … views and indexes. Materialized views
Materialized Views with Aggregates → In data warehouses, materialized views normally contain aggregates as shown in Example 9-1. For … Materialized Views with Aggregates\". Fast refresh for a materialized view containing joins and … tables upon which the materialized view is based. Here are some examples of materialized
10 Advanced Materialized Views → This chapter discusses advanced topics in using materialized views. It contains the following … topics: Partitioning and Materialized Views Materialized Views in Analytic Processing Environments … Materialized Views and Models Invalidating Materialized
9 Basic Materialized Views → This chapter describes the use of materialized views. It contains the following topics: Overview of … Data Warehousing with Materialized Views Types of Materialized Views Creating Materialized Views … Registering Existing Materialized
Overview of Materialized Views → Materialized views are query results that have been stored or \"materialized\" in advance as schema … objects. The FROM clause of the query can name tables, views, and materialized views. Collectively … term). Materialized views are used to summarize,
Refreshing Materialized Views → … Alternatively, you can control the time when refresh of the materialized views occurs by specifying ON DEMAND … Refresh one or more materialized views. DBMS_MVIEW.REFRESH_ALL_MVIEWS Refresh all materialized … views. DBMS_MVIEW.REFRESH_DEPENDENT Refresh all materialized
Multiple Materialized Views → ) GROUP BY prod_category; Multiple Materialized Views Que ry rewrite has been extended to enable the … rewrite of a query using multiple materialized views. If query rewrite determines that there is no … set of materialized views that returns all of the data, then query rewrite retrieves
Registering Existing Materialized Views → Some data warehouses have implemented materialized views in ordinary user tables. Although this … solution provides the performance benefits of materialized views, it does not: Provide query rewrite to … all SQL applications. Enable materialized views defined in one application to be
Dropping Materialized Views → Use the DROP MATERIALIZED VIEW statement to drop a materialized view. For example, consider the … following statement: DROP MATERIALIZED VIEW sales_sum_mv; This statement drops the materialized view … sales_sum_mv. If the materialized view was prebuilt on a table, then the table is not dropped, but it
Altering Materialized Views → security implications for materialized views accessed in this way are much the same as for indexes: all … . Restrictions with Materialized Views and Virtual Private Database Query rewrite does not use its … you directly specify when you create the materialized view. Altering Materialized
Types of Materialized Views → FROM clause of a SELECT statement), subqueries, and materialized views can all be joined or referenced … , such as in the WHERE clause. The types of materialized views are: Materialized Views with Aggregates … Materialized Views Containing Only Joins
Nested Materialized Views → view. A nested materialized view can reference other relations in the database in addition to referencing materialized views. … A nested materialized view is a materialized view whose definition is based on another materialized
Partitioning and Materialized Views → … Partitioning the fact tables also improves the opportunity of fast refreshing the materialized view … because this may enable Partition Change Tracking (PCT) refresh on the materialized view. Partitioning … a materialized view also has benefits for refresh, because the refresh procedure can then use … the materialized
Rolling Materialized Views → or list partitioned. PCT refresh is nonatomic. Rolling Materialized Views When a data warehouse or … tables or materialized views include a time dimension and are horizontally partitioned by the time … attribute, then management of rolling materialized views can be reduced to a few fast
Sample Schema and Materialized Views → The following sections use the sh sample schema and a few materialized views to illustrate how the … mainly refer to the following materialized views. These materialized views do not necessarily represent … this chapter. The following materialized views
Tips After Refreshing Materialized Views → re-enable integrity constraints (if any) and refresh the materialized views and materialized view … materialized view data is redundant and can always be reconstructed from the detail tables, it might be … preferable to disable logging on the materialized view. To disable logging and run incremental
Materialized Views for Mobile Computing → You can also use materialized views to download a subset of data from central servers to mobile … focuses on the use of materialized views in data warehouses. See Oracle Database Advanced Replication
Materialized Views Containing Only Joins → Some materialized views contain only joins and no aggregates, such as in Example 9-4, where a … inner join. See \"Restrictions on Fast Refresh on Materialized Views with Joins Only\" for more … information regarding the conditions that cause refresh performance to degrade. Materialized Join Views
Materialized Views for Data Warehouses → 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 … aggregations. A materialized view eliminates the overhead associated with expensive joins and aggregations
Materialized Views for Distributed Computing → In distributed environments, you can use materialized views to replicate data at distributed sites … materialized views provide local access to data that otherwise would have to be accessed from remote … sites. Materialized views are also useful in remote data marts. See Oracle Database
Materialized Views with Set Operators → Oracle Database provides support for materialized views whose defining query involves set operators … . Materialized views with set operators can now be created enabled for query rewrite. You can … marker. See \"Restrictions on Fast Refresh on Materialized Views with UNION ALL\" for
Security Issues with Materialized Views → To create a materialized view in your own schema, you must have the CREATE MATERIALIZED VIEW … materialized view in another schema, you must have the CREATE ANY MATERIALIZED VIEW privilege and the … owner of the materialized view needs SELECT privileges to the tables referenced if they are from another
Refresh Methods for Materialized Views → The database maintains data in materialized views by refreshing them after changes to their master … huge amounts of data. A fast refresh eliminates the need to rebuild materialized views from scratch … . Thus, processing only the changes can result in a very fast refresh time. Materialized views
Choosing Indexes for Materialized Views → defined on each materialized view key column. In the case of materialized views containing only joins … The two most common operations on a materialized view are query execution and fast refresh, and … of the materialized view key columns, and might need to join and aggregate over a subset of those
The Need for Materialized Views → You can use materialized views to increase the speed of queries on very large databases. Queries to … determines how the materialized view is refreshed and used by query rewrite. Materialized views … and not to the underlying detail tables. In general, rewriting queries to use materialized
Adding Comments to Materialized Views → to data dictionary views for the existing materialized view: COMMENT ON MATERIALIZED VIEW sales_mv IS … You can add a comment to a materialized view. For example, the following statement adds a comment … 'sales materialized view'; To view the comment after the preceding statement execution, the user
Benefits of Partitioning Materialized Views → Materialized views with multiple aggregate groups give their best performance for refresh and query … effective partitioning scheme for these materialized views is to use composite partitioning (range-list … on ( time, GROUPING_ID ) columns). By partitioning the materialized views this
Overview of Data Warehousing with Materialized Views → … Materialized views can perform a number of roles, such as improving query performance or providing replicated … summaries that had been defined. The database administrator creates one or more materialized views, which … . Although materialized views are usually accessed through
Using Materialized Views with NLS Parameters → When using certain materialized views, you must ensure that your NLS parameters are the same as … when you created the materialized view. Materialized views with this restriction are as follows … materialized view after a refresh operation. Expressions that generate internal conversion
Materialized View Schema Design → and you require fewer materialized views if your schema design complies with these guidelines. A … applications, so that a database administrator can create or drop materialized views at any time without … Summary management can perform many useful functions, including query rewrite and materialized
Enabling Query Rewrite → Before creating a materialized view, you can verify what types of query rewrite are possible by … materialized view so that many types of query rewrite are possible. Once the materialized view has been … query. Even though a materialized view is defined, it will not automatically be used by the query … QUERY REWRITE
Materialized Views in Analytic Processing Environments → these types of queries. It also illustrates the best approach for creating materialized views using a common scenario.
Data Warehousing Terminology → the typical work load, can be used to create materialized views. See Chapter 11, \"Dimensions\" for … fact table, and each foreign key joins with exactly one row of a dimension table. A materialized view … tables. Among builders of data warehouses, a materialized view is also known as a summary.
Overview of Materialized View Management Tasks → The motivation for using materialized views is to improve performance, but the overhead associated … following: Identifying what materialized views to create initially. Indexing the materialized views … . Ensuring that all materialized views and materialized
Table 9-2 Requirements for Materialized Views with Aggregates → Requirements for Using Materialized Views with Aggregates Table 9-2 illustrates the aggregate … requirements for materialized views. If aggregate X is present, aggregate Y is required and aggregate Z … is optional. Table 9-2 Requirements for Materialized Views with Aggregates X Y Z COUNT(expr)
Storage And Table Compression → foreign keys. This is particularly useful for materialized views created with the ROLLUP clause … Unless the materialized view is based on a user-defined prebuilt table, it requires and occupies … storage space inside the database. Therefore, the storage needs for the materialized view should be … know how much
Build Method Description → BUILD IMMEDIATE Create the materialized view and then populate it with data. BUILD DEFERRED Create … the materialized view definition but do not populate it with data.
Refresh Options → Materialized View Restrictions You should keep in mind the following restrictions: The defining … query of the materialized view cannot contain any non-repeatable expressions ( ROWNUM, SYSDATE, non … datatypes or object REF s. If the materialized view was registered as PREBUILT, the precision of the … as an eligible materialized
Using Oracle Enterprise Manager → Using the FORCE Option with Materialized View Logs If you specify FORCE and any items specified … with the ADD clause have already been specified for the materialized view log, Oracle does not return … an error, but silently ignores the existing elements and adds to the materialized view log any items … . Materialized
Build Methods → Two build methods are available for creating the materialized view, as shown in Table 9-3. If you … select BUILD IMMEDIATE, the materialized view definition is added to the schema objects in the data … results are stored in the materialized view. Depending on the size of the tables to be scanned … DEFERRED clause, which creates
Partition Change Tracking → rewrite against partial stale materialized views if partition change tracking on the changed table … not supported for a materialized view that refers to views, remote tables, or outer joins. … It is possible and advantageous to track freshness to a finer grain than the entire materialized … view.
Partitioning a Prebuilt Table → Alternatively, a materialized view can be registered to a partitioned prebuilt table as illustrated … sum_unit_sales FROM sales s GROUP BY s.time_id, s.cust_id; CREATE MATERIALIZED VIEW … materialized view was registered to use the prebuilt table. This materialized view is eligible for query
ROLLUP By Time ROLLUP By Product → year, quarter, month division, brand, item year, quarter division, brand year division all times all products Note that as you increase the number of dimensions and levels, the number of groups to calculate increases dramatically. This example involves 16 groups, but if you were to add just two more dimensions with the same number of levels, you would have 4 x 4 x 4 x 4 = 256 different groups. Also,
Components of Summary Management → Summary management consists of: Mechanisms to define materialized views and dimensions. A refresh … mechanism to ensure that all materialized views contain the latest data. A query rewrite capability … materialized views, partitions, and indexes to create. TUNE_MVIEW, which shows you
Creating Materialized Views with Column Alias Lists → Currently, when a materialized view is created, if its defining query contains same-name columns in … columns. Otherwise, the CREATE MATERIALIZED VIEW statement fails with the error messages of columns … of the materialized view's defining query and the text of user input query are identical. Thus, if … the user specifies select
Using the DBMS_MVIEW.EXPLAIN_MVIEW Procedure → The name of an existing materialized view or the query definition or the entire CREATE MATERIALIZED … VIEW statement of a potential materialized view you want to analyze. msg-array The PL/SQL VARRAY that … receives the output. EXPLAIN_MVIEW analyzes the specified materialized view in terms of its refresh
Cubes → While data warehouse environments typically view data in the form of a star schema, for analytical SQL queries, data is held in the form of a hierarchical cube. A hierarchical cube includes the data aggregated along the rollup hierarchy of each of its dimensions and these aggregations are combined across dimensions. It includes the typical set of aggregations needed for business intelligence queries.
Table 9-1 Schema Design Guidelines → SQL Language Reference and \"Types of Materialized Views\" for more information. Guideline 5 … , subject to some restrictions, is to use outer joins in the materialized view definition (that is, in the … CREATE MATERIALIZED VIEW statement). You must not create dimensions in any schema that does not … satisfy these
Query Rewrite Restrictions → Query rewrite is not possible with all materialized views. If query rewrite is not occurring when … DBMS_ADVISOR.TUNE_MVIEW to see if the materialized view can be defined differently so that query rewrite is … possible. Also, check to see if your materialized view satisfies all of the following conditions.
ORDER BY Clause → materialized views cannot have remote detail tables. Nested materialized views must have a join or … aggregate. Materialized join views and materialized aggregate views with a GROUP BY clause cannot select … from an index-organized table. Restrictions
Materialized View Logs → on top of that materialized view, which is the case with nested materialized views. For fast refresh … of materialized views, the definition of the materialized view logs must normally specify the ROWID … clause. In addition, for aggregate materialized views,
Loading Data into Data Warehouses → QUERY_REWRITE_ENABLED = FALSE statement until all the materialized views are refreshed. If … session level to any users who do not require the materialized views to reflect the data from the latest … modes that only materialized views with updated data participate in a query rewrite.
Refresh Mode Description → automatically at commit time. You can specify how you want your materialized views to be refreshed from … ON COMMIT Refresh occurs automatically when a transaction that modified one of the materialized … view's detail tables commits. This can be specified as long as the materialized view is fast … DBMS_MVIEW package