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| Database Management Series |
Apart from the various versions of SQL ANSI standards, each RDBMS vendor takes the liberty to implement its own solutions in accordance with the problems it’s trying to address – performance, parameterization, partitioning, distribution or whatever other problem might arise. There are several types of views evolved from such attempts, several other names being mentioned in database literature:
Union view – view based on the union of one or more database objects.
Join view - view based on the join of one or more database objects.
Hierarchical view – view based on hierarchical relationships processing techniques.
Base view – view consisting of all of the rows from a table and a subset of columns.
Derived view – view created from a base view by selecting only a subset of rows.
Projection view – in NetWeaver, view used to hide the fields of a table, containing one table and all its rows [1].
In-line view – it’s a “pseudo view” and refers to (in-line) self-contained subqueries used inside of other queries, without actually defining a view. The query can be run independently from the query in which is contained.
Updatable view – views that allow data changes on the tables they are based on.
Maintenance view – in NetWeaver, view that allows viewing and updating data from a set of tables that form a logical unit [1].
Object view - virtual object table based on user-defined types that allow conversion of relational tables into object-relational tables, facilitating thus the use of object-oriented programming techniques without converting existing tables, and the consumption of relational data by object oriented applications [3].
Federative view – view in a federated database system, a meta-database which integrates multiple autonomous database systems.
Consolidated view – view which provides data in a form more frequently required by users [4].
Indexed view or
materialized view – is a virtual table that allows storing the output of a query, being ideal for aggregating data across multiple rows, the values being updated and materialized, being queried without continuous recalculation.
Regular view – view that stores no data, as opposed to an indexed view.
Parameterized view – is a view which, much like a function or stored procedure, accepts a set of parameters that dictates the output. In SQL Server parameterized views are implemented with the help of inline table-valued functions.
Partitioned view – a view formed by the union of more tables with the same structure and found within one or multiple autonomous SQL Server instances.
Distributed-partitioned views (DPV) – are portioned views working across multiple instances
System view – refers to the views used by RDBMS vendors to expose metadata about their systems. For example MS SQL Server exposes several types of system views:
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catalog views – return Database Engine related metadata, according to BOL they are the “most efficient way to obtain, transform, and present customized forms of this information” [2].
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information schema views - "provide an internal, system table-independent view of the SQL Server metadata", which “enable applications to work correctly although significant changes have been made to the underlying system tables” [2].
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compatibility views – views implementing backwards compatibility functionality, implemented previously within tables.
• replication views – views based on replication system tables used for implementing SQL Server data replication.
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dynamic management views - "return server state information that can be used to monitor the health of a server instance, diagnose problems, and tune performance" [2].
System internal views - "views that make available low-level storage metadata for the SQL Server Database Engine" [2].
Help view – implemented in NetWeaver, a help view it’s not a typical database view, being based on a primary table and a search table used in NetWeaver’s online help system.
Conceptual view – concept-based view in a conceptual data model which maps the concepts and relationship between them.
References:
[1] SAP. 2009. SAP NetWeaver 7.0 Views. [Online] Available from:
http://help.sap.com/saphelp_nw70/helpdata/en/cf/21ecc5446011d189700000e8322d00/frameset.htm (Accessed: 2 November 2009)
[2] MSDN. 2009. SQL Server Books Online. [Online] Available from:
http://msdn.microsoft.com/en-us/library/ms130214.aspx (Accessed: 4 November 2009)
[3] Oracle. 2000. Chapter 14: Object Views. Oracle 8i Concepts. [Online] Available from:
http://www.cis.unisa.edu.au/LearningResources/oracle/server.815/a67781/c13obvw.htm (Accessed: 4 November 2009)
[4] Sybase. 2009. Consolidated views. [Online] Available from:
http://infocenter.sybase.com/help/topic/com.sybase.help.sqlanywhere.11.0.1/dbreference_en11/views-s-4117677.html (Accessed: 2 November 2009)
