View (SQL): Difference between revisions

Revision as of 16:43, 3 December 2017

Revision as of 16:44, 3 December 2017

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Some systems support the definition of INSTEAD OF [[Database trigger|triggers]] on views. This technique allows the definition of other logic for execution in place of an insert, update, or delete operation on the views. Thus database systems can implement data modifications based on read-only views. However, an INSTEAD OF trigger does not change the read-only or updatable property of the view itself.

==Materialized views==

==Advanced view features ==

{{details|Materialized view}}

Various [[database management system]]s have extended the views from read-only subsets of [[data]].

Various [[Oracledatabase Databasemanagement system]]s introducedhave extended the conceptviews from read-only subsets of [[data]], particularly [[materialized view]]s: pre-executed, non-virtual views commonly used in [[Data warehouse|data warehousing]]. They give a static snapshot of the data and may include data from remote sources. The accuracy of a materialized view depends on the frequency of trigger mechanisms behind its updates.

Materialized views were introduced by [[Oracle Database]], while [[IBM DB2]] provides so-called "materialized query tables" (MQTs) for the same purpose. [[Microsoft SQL Server]] introduced in its 2000 version indexed views which only store a separate index from the table, but not the entire data. [[PostgreSQL]] implemented materialized views in its 9.3 release.

== Equivalence ==