Materialized views in relational databases are a type of database object that store the results of a query physically, much like a regular table. Unlike standard views, which are virtual and generate their data dynamically each time they are accessed, materialized views maintain a copy of the query results on disk. This allows for faster data retrieval because the database does not need to re-execute the underlying query every time the view is accessed. Instead, the database can read directly from the stored data, significantly improving performance for complex queries or large datasets.
One common use case for materialized views is in reporting and analytics scenarios. For example, a business might need to produce regular sales reports that aggregate data from multiple tables. Instead of running a complex join query every time the report is needed, a materialized view can be created to store the aggregated sales data. This allows the report to be generated quickly, as the database simply accesses the pre-computed results. Additionally, materialized views can be refreshed periodically to ensure that they reflect the most current data, which can be set to happen automatically or at specific intervals, depending on the application's needs.
However, it's important to consider that materialized views come with trade-offs. While they provide fast access to pre-computed data, they also consume additional storage space and may require maintenance. Specifically, whenever the underlying data changes, the materialized view must be updated to reflect those changes. Depending on the implementation, this can be done immediately or in a delayed manner. Developers should weigh the benefits of faster access against the costs of ongoing maintenance and storage when deciding to use materialized views in their database designs.