For example, it may be a local copy of data located remotely, or may be a subset of the rows and/or columns of a table or join result, or may be a summary using an aggregate function.
[4] Materialized views that store data based on remote tables were also known as snapshots[5] (deprecated Oracle terminology).
Materialized views find use especially in data warehousing scenarios, where frequent queries of the actual base tables can be expensive.
Materialized views were implemented first by the Oracle Database: the Query rewrite feature was added from version 8i.
[15] MySQL doesn't support materialized views natively, but workarounds can be implemented by using triggers or stored procedures [16] or by using the open-source application Flexviews.