16 High-Function Business Intelligence in e-business
2.1 Materialized view overview
In this section, we describe:
Materialized view motivation
Materialized view concept overview
Materialized view usage considerations
Materialized view terminology
2.1.1 Materialized view motivation
Before we explain what a materialized view is, let us discuss the motivation for its
introduction.
In a data warehouse environment, users often issue queries repetitively against
large volumes of data with minor variations in a query’s predicates. For example:
Query A might request the number of items belonging to a consumer
electronics product group sold in each month of the previous year for the
western region.
Query B may request the same kind of information for only the month of
December for all regions in the USA.
Query C might request monthly information for laptops for all regions in the
USA over the past 6 months.
The results of these queries are almost always expressed as summaries or
aggregates. The base data could easily involve millions of transactions stored in
one or more tables, that would need to be scanned repeatedly to answer these
queries. Query performance is more than likely to be poor in such cases.
Materialized views were introduced to address the aforementioned performance
problems.
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