What is the process of rejoining relations that were decomposed during normalization?

The process of rejoining relations that were decomposed during normalization is referred to as denormalization. In database design, normalization involves breaking down a database schema into smaller, more manageable relations (or tables) to eliminate redundancy and improve data integrity. However, in some situations, these decomposed relations may be rejoined or merged to improve query performance or simplify data retrieval. This merging process is known as denormalization.

Denormalization can be beneficial in scenarios where the performance of data access is more critical than the space efficiency of the database. In practice, denormalization might involve duplicating certain data across tables or combining multiple tables into a single one to reduce the number of joins required during query execution. This can enhance performance but may introduce redundancy and can complicate data integrity maintenance.

Normalization and entity-relationship modeling refer to the processes of organizing and structuring data and relationships during the initial design phase, while data abstraction involves hiding the complexities of the database from users, which is not directly related to rejoining decomposed relations.