Can you give examples of situations where database denormalization is justified and beneficial?

Denormalization of a database is justified and beneficial in the following situations:

• Improving read performance: When the system frequently performs complex JOIN queries, denormalization allows related data to be stored together, reducing the number of joins and speeding up queries.
• Avoiding redundant calculations: If data is often aggregated or computed on the fly, it can be pre-stored in a denormalized form.
• Reducing database load: In systems with high read load, denormalization helps decrease response time and server load.
• Simplifying caching: Denormalized data is easier to cache since it contains all necessary information in one place.

However, it is important to remember that denormalization increases data maintenance complexity, as synchronization and updating of redundant data are required when changes occur.

Example: In an online store, instead of storing product and order information in separate tables with JOINs, a copy of the product information can be stored directly in the order record for quick display of purchase history.