In this recipe, we will see how to increase the performance of the database—especially in a data warehousing environment—but the same recipe can be used with small changes in an OLTP environment as well by using materialized views.
Materialized views can be seen as snapshots of the data in one or more tables, on which a computation has been applied, for example, a join or a group. This summary data can be used to answer client queries readily, instead of reading all the data in the original table(s). An example is worth a thousand words. For example, we have a SALES table in SH schema, containing around 1 million rows, and we want a report of sales by product. We will see how materialized views, in such cases, can help a lot in reducing access to the database, specially the I/O.
