Materialized views are similar to views because they also depend on other tables for their data, although there are a couple of differences. SELECTs against views will always fetch the latest data, whereas SELECTs against materialized views might fetch stale data.

The other key difference is that materialized views actually contain data and take up storage space (proportionate to the volume of data), whereas views do not occupy significant space on disk.

Materialized views are used mostly to capture summaries or snapshots of data from base tables. Some latency/staleness is acceptable. Consider the case of a report for average branch-wise balances for a bank at the end of business day. Typically, the report will be sent after close of business for the day, implying that the averages, once calculated, are not likely to change for that particular day. In addition, no one is likely to request the report before close of business.

For a website, reports displaying average and peak...