Materialized Views

A materialized view provides access to table data by storing the results of a query in a
separate schema object. Unlike an ordinary view, which does not take up any storage
space or contain any data, a materialized view contains the rows resulting from a
query against one or more base tables or views. A materialized view can be stored in
the same database as its base tables or in a different database.
Materialized views stored in the same database as their base tables can improve query
performance through query rewrites. Query rewrite is a mechanism where Oracle or
applications from the end user or database transparently improve query response
time, by automatically rewriting the SQL query to use the materialized view instead of
accessing the original tables. Query rewrites are particularly useful in a data
warehouse environment.