What is the purpose of database normalization? How to determine how normalized the schema should be?

Database normalization is necessary to eliminate data redundancy and prevent anomalies during update, insert, and delete operations. It helps structure data so that each table corresponds to a single entity, and relationships between tables are clearly defined.

The degree of normalization is determined by balancing performance and ease of maintenance. Typically, the goal is to achieve the third normal form (3NF), which eliminates transitive dependencies and redundancy. However, in some cases, such as to improve read performance, denormalization is allowed — a deliberate introduction of redundancy.

Deciding how much to normalize a schema depends on data integrity requirements, the frequency of read/write operations, and query complexity. If data is frequently updated and integrity is crucial, higher normalization levels are advisable. If read speed is the priority, normalization can be sacrificed for optimization.