Denormalization

Denormalization is deliberately adding redundant data to a database, or merging tables, so that common reads need fewer joins and run faster. It is the reverse of normalization and is applied after a normalized design proves too slow for a workload.

Examples are storing a customer's name on each order row, keeping a precomputed order total, or maintaining summary tables for reports. The cost is extra storage and the work of keeping copies consistent when data changes, often done with triggers, application code or materialized views. Data warehouses and NoSQL databases are commonly denormalized.